Billies offer a much better dampening than the standard strut IMO
ride quality is slighty harder when run with standard springs, and a fair bit harder when run with lowering springs. So its really down to your spring choice
Billies are slightly harder but give a much more supple ride and don't crash over holes etc, they are so much better than standard shocks. As someone else (can't remember who sorry) said they give a german car like ride.
have a search one of the guys gives a break down of different suspension setups and how they felt/performed.