Hi Annie,
Quite a few people have replied to your post already, and a lot of valid statements and arguments have been made.
Having said that, this is really about one's personal experience, so if you don't mind, allow me to elaborate a little on my train of thoughts in the digitalisation process, and the move to MFT, or the addition of MFT to one's arsenal.
As mentioned by others, 12-100 is a very good general purposes lens, although with generally not enough reach for wildlife, so you may want to consider other, longer lenses, possibly even older FT lenses (with adapter), like the 50-200 SWD, which is a favourite lens with many MFT wildelife shooters out there.
Just check out some of the photographs of "the black fox", who posts here, but also on photography-on-the-net, in the Oly forum over there.
An alternative lens may be the Panny 100-300 as well, the older version (Mk I) may possibly be had for a reasonable amount, and may well give you plenty of possibilities to try stuff out to start with.
Fuji cameras aren't really that small, IMO, and in that case you might just as well stick with the Canon SL1 you have or had, which actually has a slightly better cropfactor for wildlife. Neither are the Fuji's wildlife lenses better or lighter, much of a muchness really when it comes to Canon, although the Canon 100-400L is truly a great lens.
Personally, I never changed as such from FF to MFT, as got into it as an additional system, as they both have their uses. I started off with a Canon G5 back in 2004, and when the EOS 350D came out a bit later, I got one in 2005, when the price dropped to a level I was willing to pay. A few years later I moved to a Canon 5D, and realized I should have gotten one straight away when I got the 350D - would have saved me money if I had done so
. Within a year I moved on to the 5D II, which I used a lot until a year and a half ago.
In 2011 I was fortunate in that I could get a complete set of MFT gear for a very reasonable price, essentially a Panny GF2 with a 14-140, 7-14 F/4, 14 F/2.5, 20 F/1.7, and PL 45 F/2.8 Macro. This was great, because of my travelling for work meant I could not always bring the FF stuff along, just too big and heavy, or taking up too much space.
I did want a full-fledged, similar system to my Canon FF one, however, so I started collecting a bunch of lenses, basically to match my Canon stuff, and to be able to select different sets of lenses for travel, to be able to choose anything from a very light and (almost) pocketable set to a realitively heavy one for MFT, replacing the GF2 with an EM-5 Mk II at first, followed by an E-M1 II a bit later, and finally a Pen-F to replace my G10 I replaced the G5 with, for a similarly sized camera allowing interchangeable lenses.
I really like the Oly stuff, because the images, apart from the format, have a similar rendering OOC as my Canon ones have.
And just like with Canon, you can actually get good shots straight OOC, without learning if need be, although I would suggest you keep on doing so regardless. In order to get the best out of one's tools, one has to learn and understand them, it needs to become second nature to use them. That will only happen by using the tools, by learning how to use them, and by learning how you prefer to shoot yourself. And that never really stops if I may say so after using cameras for almost 58 years
.
What is wrong with still needing or having to learn?
The learning process never really stops, and the advantage of digital is that you can experiment without the cost of having film processed and printed, which, especially if you do that yourself, takes up not only more money, but also more time, apart from being able to see results instantly.
What I used to do, and still do to this day, when shooting for myself in the first place, is imagine the image I want to create, and work towards that. The advantage of digital here is that you could in principle take as many shots as you like, with slightly varying shutter speeds, apertures, iso values, view angles, etc. - this is where you learn. With analog that was a lot harder
.
More functionality in a camera also means more to learn, BTW
.
I am a pixel-peeper to some degree as well, not extreme, but as a perfectionist I like to have everything as good as can be, although I tend to stay practical
. As to IQ, what is important is how
you define IQ. That is really something to ponder thoroughly, and only something I figured out consciously many years after starting with photography, although I always made steps in that direction intuitively.
For me, IQ has to do mostly with rendering, colours, ideally edge to edge sharpness and the correct viewpoint and AoV for a particular image I have in mind. Noise I find less important, because I have shot a fair amount with Tri-X upped to 1600 iso in the past, and know what one can expect, and still create great looking photographs
. However, all of this is very personal, and the only way to find out what you personally find important in IQ is by really figuring out what it is you really like in your own photographs, from both a technical and emotional perspective.
I am lucky in that I have more spending money available than I had in my early days in photography, which means I can choose and select, to a degree, the lenses (and cameras) I really want to use in order to achieve the results I have in my mind's view. However it is also important to think about what an image is for, what you want to achieve with it. There is a big difference between a limited size jpeg for use on the internet, and a large size print to hang on a wall. And personally, I spend much more time on perfecting an image which wil hang on a wall than an image that will only be displayed on a monitor.
Creating a perfect image, for your view or opinion, always comes at a price, and time spent learning is in that case not optional
.
When switching to MFT, I did have about 6.5 years of experience with digital, but way more with analog. To be very honest, I do think that the same rules apply, just adapted to a different medium, that is really all there is to it, and it is the same going from analog to digital.
I have never been frustrated using an MFT camera at all, other than that I would possibly want different lenses than the ones I had available for specific types of shooting. By now, about 9 years later, I do have them all barring one, which is really not available yet, but which I do not miss a lot considering the good glass I am lucky enough to own. Some lenses will never be available for MFT (tilt-shift lenses come to mind), but a good adapter or speedbooster does make it possible to use such anyway. That is another reason to keep on shooting 2 systems, or more if necessary, as each system has different uses, possibilities and options, which may not all be right for different reasons or times.
Advancing one's skills, by using manuals, or this (very helpful and friendly) forum, is relatively easy, but it stops at the point where you actually have to go out and do it yourself. And that is the best way to advance your skills. Learn from what you do, analyze the results, to see where you could improve, where you want to improve, and set out deliberately to do so. That in the end is the only way to advance. It is also the only way to develop your own style. Similarly, study photobooks, go to museums, learn from those, analyze what you like and why.
Would I do it again, the same purchases? For MFT, almost. The initial setup I got as a "starter set" suited me to a t. When I got the E-M5 Mk ii I probably should not have gotten that, because I really knew that I wanted a newer sensor with some more MP, which is why it did not last too long in my toolbox. Neither should I have bought the GM5 I got, because it was a throwback in a way, to the rendering I did not like too much, and really too small a camera for me. Then there was the Oly 60 Macro - I never really got along with it, so I should have investigated that more, but otherwise I am fine. I deliberately got a few lenses double, not only aperture-wise, for different sets to carry when the need arose, but also to see the differece, like equivalent Panny and Oly lenses. By now I have weeded out what I like and do not like, so it will stay like that for a few years to come I suspect. It really is and was a voyage of discovery
.
As to my FF setup: the EOS R replaced my ageing 5D II, and I am very happy with it, it truly is a great camera for me. The path to FF is something I should have done differently, as mentioned already. I should really have skipped APS-C completely, with hindsight. I learned a lot with the different cameras I had (350D, 400D, 40D) and tried out (450D, 600D, 50D, 60D). I really only became a happy camper with the 5D and 5D II back then, but I am just as happy with my FF as with my MFT setup, in that they overlap when need be, for different purposes. Lenswise I have no complaints, I followed a predetermined path based on my experience with analog and my favourite topics to shoot, and I also had the opportunity to try and test many other lenses.
Anyway, these are some of my thoughts on the subject, and I do hope they make some sense for your questions.
HTH, kind regards, WIm