>>4273992then you'll be getting subpar low light performance (you moaned that f2 is too slow). remember: the fstop is always relative to a lens' nominal focal length (not the equivalent focal length!).
f2 on full frame is equivalent (in terms of amount of light getting through the lens) to a f3 on APS-C and f4 on MFT when you want to have the same field of view.
a full frame 50mm f2 will have an opening of 25mm, an apsc 34mm will have an opening of 17mm and a 25mm m43 lens will have an opening of 12.5mm.
those lenses all have the same field of view but you will be getting the most light from a full frame lens. (big window lets in more light than small window)
so if you go with anything lighter you will have to deal with more noise. if you can live with that: fine. (I myself have a m43 secondary body because I don't dislike noise). but if you're one of those low noise uber alles people then you will have to schlepp around a FF body+lens or be unhappy with apsc/m43.
