I used to get ALOT of hand numbness while road-riding on my mtn bike. In Fact, after one LONG ride, I had ulnar nerve palsy for a week - the numbness persisted b/c I had so irritated/compressed the nerve during the ride.

I now have a road bike and I find that the drop bars offer me numerous options for change of hand positions. I haven't had any major numbness w/ the drop bars. I also agree about core strength. As my abs and back get stronger I find that I can take more of the weight on my hips and on the pedals and don't have to lean so hard on the handlebars.