Originally posted by luftfluss You quoted me talking about sensors, but you're talking about lenses... so, I think I'm going to drop out of this.
Do what you'd like, but you talked about both lenses and sensors in that post.
The pictures, as you know, are a product of both.
If you have the money for the top lenses (that can resolve good enough for a small sensor, and are fast enough for a small sensor) there's almost no difference between the two sensor sizes.
Currently there's several Voigtlander, etc lenses that, when paired with a M4/3 camera, can make pictures like an APS-C camera.
In my experience, if you're comparing, say, sub-$500 lenses, you're going to see a big difference between APS-C and M4/3.