I might be a nOOb to this whole thing, but I would say a good thing to consider when choosing a bur would be to think about what you are wanting to accomplish.
For an amalgam a 330 will allow you to provide adequate resistance/retention with little effort, eg, the inverted pear shape gives you converging walls. Moreover, in preclinic its length (1.5mm) will give you a great guide for depth in your prep. However, say in a Class II situation a 330, IMO, will be difficult to see interprox. I would use a 245 here
For composite where retention is not as important I would go diamond, cuts faster and the last longer.
Inlay/only preps need divergent walls, hence a 330 will require a little more work. It has been a while, I cannot remember what my bur of choice was!
Crowns, veneers ect. are a whole new can of worms
My, avoiding studying, two cents,
-C