They both have their ups and Downs. Personally I like adw better, but that's also because i got used to adw faster. Now if launcher pro had specially designed docks(not just an overlapped image) than it would be the clear cut winner. Just like of adw had Widgets...it would be the winner. I think launcher pro gets a bit more love because it IA Tue most well known. If more people jump on adw and balance out the love...then adw could become king. One of adws other downfals is that most of the themes cost money and I believe people are scared by that when launcher pro essentially has free themes. Although I believe the themes are fully worth it. Some are generic but for the most part each one has its own style and makes the OS look different each time.
But this is simply my opinion. I switch between the two a lot but mainly stick with adw. Although right now I'm using touch wiz.
Adw with theme two in blue/black