DBP has everything dbc has plus: vertex and pixel shaders, BSP map support, Environment effects, light mapping, bump mapping, real-life projected shadows, LOD terrain, cartoon shading, reflective shading, MDL & MD3 support (not on current patch, but to return), multiplayer (w/o buying dark matter), multi-texturing, Windows style IDE with color coded text, enhanced program settings, bone anims, eons faster 2D sprites, - require a 3D engine though, but who doesn't have one these days?, more data types including WORD, DWORD, Boolean,; Create Modules, Extend the language with DLLs!, etc....
The IDE is far superior in my opinion, but DBC does have a downloadable win IDE that is very similar. I haven't tried it yet, but hear good things about it.
Known bugs in DBC: none
Known bugs in DBP w/ latest patch (that i have found):
Turn, pitch, roll errors; xyz rotation errors when attempting free flight; Buggy variable types (for added types such as WORD, DWORD, Boolean. Older types such as floats, integers, strings have no known problems), Multi-Texturing whether using bumpmaps, lightmaps, and others have what appears to be a pointer error which will only display one map on all objects using Multi-Texturing. Ghosting error which will not show objects created after an object is created through transparent selections (mostly noticeable in Alpha-Texture maps good for windows, water, and such). Possable animation problems (ie syncing on slower machines). Others I don't know of....
Though this list is a long list of bugs, they are getting squashed more and more. We are all anticipating Patch 5 to clear much of this up. Another thing on bugs, the new patch 4.0 created a whole new 3D pipline and thus is buggy. The idea of patch 5.0 is to clean all that up as well as clean up a lot of stuff that patch 4.0 never touched that might be a little buggy or just not fully implemented... by the way, where they heck are all the new commands especially for LOD terrain? Eh.... they'll get here. Matricese take care of that for now at least.... Another thing about bugs, some of the bugs are encountered via strange external files (such as 3D objects and bitmaps), many people of the community have created programs in their spare time to deal with some of these incompatabilities, such as the Truespace UV mapper that fixes object materials that I have made. You can find many of these under resources on this site.
DBP also ships with a free kitten in a brown package!
(well, that might have been an exageration)
Current Projects: mini BSP maker 50%, Height Mapper with many features 75%, FPS/RTT Nameless at the moment 15%
