In terms of noise in RAW files, the OMD at 400 is very close to the EP2 at 100. EP2 looks just a tad bit better. BUT, the OMD looks a little bit sharper and also has more resolution. Downsize the 16 mp file to 12, and the noise level advantage of the EP2 at 100 would likely disappear or decrease. So arguably, the OMD may have a two stop advantage (although I'd guess more like one stop) . Unfortunately, DPR doesn't have RAW sample photos of the EP2 above 100 to look at it more closely. But looking at the EP1's RAW samples, I think there's at least a one stop stop advantage of the OMD RAW files over the EP1, if not close to two.
As for dynamic range, I agree that it's hard to tell from the sample photos.