I started with DBC, I don't think I remember knowing Pro existed when I bought it, may be it didn't - what was the release date of pro?
I got some good stuff in DBC (nothing ever completed: this was before joining the forum), but collision was my main problem, however I found it was when moving to Pro as well, but later I've learned the plugins that help. The switch from DBC to DBP was good, it left me with a lot more options.
But DBP doesn't have the demo nor the help-package DBC had, which I found quite useful. Conversely, with DBP, we have a lot of help with the forums and code snippets laying around anyway.
I was lucky with DBP, Amazon was having a sale and gave it away for £15, plus it was still when DBP came in cardboard packaging.
I love the app: in ALL of my attempts to try something different, something more powerful and faster than it, I find myself coming back.
My advice is that if you have the money to spare, get Dark Game Studio - so you get pretty much everything you need.
But needless to say, there are even some great DBC collision tutorials around, it might be worth looking them up. I believe there were some on the main TGC site.