Christmas present to myself, maybe

[Compass Rose]

Will this be your 1st SB title?

From your list I would highly recommend Korea, Pacific War, and RV as they are all very good games.

RV is arguably the best well-put together SB game currently available.
PW (Pacific War) will give you a totally new experience in fighting with caves and island warfare.
KW (Korean War) is also a good game that still uses alot of WWII weapons.

I don't play against the AI, so I'll save that part of your question for someone who does.

Whether you pick RV, PW, or KW, you will be picking a good title and will have alot of good PBEM battles ahead of you.