Ergon grips that I prefer on my MTB bars are too wide and make it harder to get my thumb down and then up under the hand position. So I have to go with a more traditional round grip.
I've experimented with several grips and haven't found anything that eliminates numbness the same way that the Ergons do. Here's my next attempt. My buddy, Jason, runs the ESI's and I really like the potential.
Get out there.