Hi Douglas
I completely agree with this - the difference in sensor size really isn't such a big deal . . . the difference I see is that Sony are making much much better sensors than Panasonic. That, and the fact that Olympus seem to be simply refusing to make the compact professional quality body that the E1 suggested is the only thing that keeps me out of 4/3 at the moment; the lenses are always the lure back on board.
Actually, if Panasonic built an APS-c sensor and Sony a 4/3 sensor I'm willing to bet that the Sony 4/3 would still show real advantages over the panasonic APS/c
The 4/3 sensor is 13.5mm high, the APS c is 16.7mm this really isn't so much!
Main issue is, that the sensor in the E5 is only the already aged 12MP version. If it would be the latest 18MP version of the GH2 results would be MUCH better, as I can tell from the results of the GH2. I cannot say if better than the latest APSC Sony sensors, but pretty much the same till 6400.
Actually I think all this ISO peeping is same as pixel peeping, who really needs it? look at the M9, its max. sensitivity is ISO2500 and it delivers better results than a Nikon D3S or D3X just because of the lacking AA filter and the reason that if higher ISO levels are not available people start thinking how else they can get great results in available light - also called creativity!
While I had the E5 for testing I also compared it at same moderate ISO level to the D700, which actually one would call an unfair comparison, just because of the differences in sensor size. But actually I liked the results from the E5 more up till ISO1600, much more natural compared to the very "plastic" look of the D700, already in the range of ISO1600. Of course the E5 is more grainy, but actually I found I prefer the more grainy look compared to the more clinical plastic look of the D700. And the Zuiko Pro grade lenses are definitely superior to the Nikkor counterparts.
Then at ISO 3200 and 6400 the D700 wins in most situations, but this is for the price of an even more "plastic" look. I agree that in some cases the ISO6400 results from the E5 are not even useable anymore, but end of the day in most situations when using the Zuiko high speed zooms (2.0) and limit below ISO 3200 I like the Oly results much more.
Had Olympus only used the new GH2 sensor in their E5, this camera would have been the absolute killer DSLR and no discussions necessary