It depends.
FPS Creator is made with DBPro. It's a prebuilt framework so you don't have to do a lot of the work yourself to create modular maps, entities, and all the other stuff crammed in there.
So the big question then is, does FPS Creator have everything you need to bring your game to the level you want?
If it does, then you are set.
If it doesn't, then you have to decide if you can do it better in DBPro, or maybe you'll want to use the newly released source for FPSC and modify that to fit your needs.
I've resisted FPSC so far, but I am starting to see it's merits, and I've been considering an FPS project recently.