Personally I haven't noticed any differences with bars. That's because bent elbows will have the upper-arms leave the chest at exactly the same position, so you shouldn't feel any differences.

You gotta protect the bike!!! Road-rash will heal, but bikes costs money! Practice turning your shoulder towards the attacker and steering your bike away. Then right before you impact, lean into them to give youself a little more momentum to shove them out of the way. Really handy for sprints at the end of the race...