Get this-->
http://www.darkgamestudio.com/bonanza.php
I just got back into DB programming (used to play around with DB Classic). The question really boils down to this I think: are you comfortable with tackling learning C/C++? The basics of C/C++ are not too dissimilar to BASIC, but memory management is more of an issue. If you're unsure, I'd go for the DGS Bonanza deal. GDK is free anyway, might as well get the Physics, Lights, Shader, and AI plugins as well as DBPro for super cheap. I primarily use DarkGDK, but I'm definitely excited for DBPro to arrive in the mail--nothing beats it for a quick prototype.
For your specific questions, GDK has a slight edge in performance, but of course is more difficult because it is in C (unless you've written code in C before, then you might love leaving the ambiguity of BASIC).
In terms of help and tutorials, they are nearly identical. Any code you see in DBPro can be converted to darkGDK by removing all the spaces between the parts of commands, adding parentheses and a "db" prefix and semicolon suffix.
ie: "Sync Rate 0" becomes "dbSyncRate(0);"
Code written for DarkGDK may or not be easily converted to DBPro, it all depends upon whether or not the programmer has taken advantage of C++'s object-oriented programming features.
DarkGDK wins for me primarily because of the fact that you can use it in C++, and as such all the object-oriented programming features that come with it. However, if you've never read anything about object-oriented design, it will probably be of little use to you until you have a little more programming experience under your belt.
A third option is DarkGDK.net, in which you get a managed programming environment that you can use in C# or VisualBasic.NET. These both still have object-oriented programming features, but are "managed" and thus take care of lower level things such as memory management for you, and also give you access to the .NET framework which is full of a lot of useful programming utilities that allow you avoid having to deal directly with the Windows SDK as well as provide tons of other useful functions.
