@demiro
It's a fairly complicated subject, but I will see if I can provide some kind of overview about the positives and negatives of what's available on the market. Keep in mind I'm referring to general audio recorders, and excluding body pack recorders.
The lowest priced stuff on the market (Zoom H1n etc) has the benefit of being cheap and small, but comes with a few limitations that can be a hindrance depending on your needs. Imo the biggest limitations are they rely on built in microphones, or 3.5mm (1/8") TRS jacks, and the premaps aren't that good. If you can get close to the source and get a good strong signal they can be really good. However, if you have to apply any appreciable amount of gain you will get a lot of self noise from the preamps. Only supporting 3.5mm inputs limits your external mic options, to Lavs, wireless lav receivers, or camera top type mics.
The main benefit of the larger and more expensive handhelds like the Zoom H4 and H5, are XLR and 1/4" inputs, as well as a wider range of recording codecs, bitrates, and same rates. You also start getting the ability to do safety tracks and some amount of mixin in the device. The main limitations are still the preamps, and battery life if you are using phantom power. The zoom H4n Pro is supposed to have better preamps than its predecessors, but they still aren't as good as what you get in higher end models.
As an aside I think the high end handhelds like the Zoom H6 & H8 are a waste of money. They are trying to shoehorn bag style recorder functionality into a handheld device. when you start feeding in multiple external mics, you end up with cables getting in the way, and you burn through batteries really quick. Not to mention they cost as much as the lower end bag style recorders.
I personally separate the bag style recorders into 2 categories, prosumer and pro. Imo, prosumer is the $300 to $1k range, and pro is everything above$1k.
You have to be careful and do a lot of research when you get into the prosumer segment. The preamps are generally all pretty good. The major differentiators are the number of inputs, timecode support (and how good it is), external power support, and then how flexible are the sampling, recording, and mixing features. other nice features are dual card slots, and seamless switching between internal and external power.
For example you can get a Tascam DR-70D for $300, but you can't trust its internal clock for timecode out, it needs to be driven by an external timecode generator like a tentacle sync. On the plus side you can power it with AAs internally or externally via usb or a wall wart.
I personally have a Zoom F4 (no longer sold) and love it, because its internal timecode clock is very good, and it can be powered externally via a wall wart, or a locking 4 pin hirose connector.
The down side of bag style recorders, is that you have to use an external mic, and thus you have extra cost, and cables to deal with.
Depending on your setup, something you might want to consider is a camera preamp/ audio adapter. I used a Saramonic SR-PAX2 (~$150) for a while and got good results. You can use external mics, or you can feed it line level inputs as well.