I have two systems: Nikon D7100 and E-PM2 Other than wide angle lenses, I currently have a Nikon 85mm f1.8D for Nikon mount, and a Leica 45mm f2.8 macro and a Sigma 60mm f2.8 for Olympus mount. (My wife is using her own D300, 105mm f2.8 VR Micro and some other shorter lenses.) Now I am planning to get a fast telezoom lens. (Not getting any f5.6 lens.) I mainly shoot indoor events, and very much prefer the performance of the Nikon than the Olympus. Moreover, I don't have a proper flash unit for E-PM2. However, I rarely (but may) shoot with flash with a telezoom lens. Price aside, if I buy a telezoom lens for Nikon mount, it will be be very heavy and bulky/long. If I buy a telezoom lens for Olympus, I will not need to switch wide and tele lenses on my Nikon body since I can bring two bodies out (i.e. Nikon + Olympus). Hope to get some advice. Thanks.