For a DD, there's not that much difference. 2011 Nismo#91's ~3.3% less for E10 should be in the ballpark for MPG and power should be close to the same. For reference,
E85 is ~30% less.
Butt dynos are notoriously inaccurate. I'm not sure my butt would be able to feel 3% difference. It could be that you are running rich/lean and the E10 is burning better, but that's just a SWAG. I'm betting it's just a perceived difference.
Personally, I try to get "G100" whenever possible but don't get upset if I have to use E10. I might do the next fillup a little early but don't consider it to be a big deal.
E85 is a different story. I avoid it except when it's all that is available at the time. I will get just enough to get me to a real gas station.