i found the multi-touch aspects of milestone vs dolphin to be fairly comparable. Milestone might be slightly more refined but honestly it's hard to tell the difference. I forget if dolphin had the double tap to zoom, but if not, thats one place the milestone beats out doplhin (my bad if dolphin has the double tap, i know you can long press to bring up that menu). Other than that, I don't like the ads of dolphin but not a big deal. I always prefer a "stock" app to a 3rd party one IF they are comparable in functionality and here they are. I like the stock bookmark layout as well in compared to dolphin.
I'd say overall they are pretty darn comparable, but the milestone one win's slightly all around for me all around.