either ya need to work on hand strength or something's wrong, either the position or mechanics. Talk to the LBS cuz you shouldn't have trouble braking. If you have small hands, I've heard campy is better for that, so don't buy 105 if that's the issue.

I rode Sora for a year,upgraded to ultegra recently and ultegra braking isn't better... cuz I found nothing wrong with sora.