Thank you Sailor Steve, what a great, comprehensive way to start and guide the responses. Initially, my intent is to just get the ball rolling and not worry to much about super realism. That being said, I'm not looking for arcade mode either. I remember SH4 fondly, and yes 4WP was meant to indicate Wolves of the Pacific. Someone else recommended SH3 for its smaller theater of operation, making it easier to get "stuck in". Like anyone I do want the best visual experience I can get, but that is certainly second to quality of game play.
I do like the progression of quality of subs, starting small and graduating up the line, that has it's rewards. Is SH5 still a FPS kind of experience or is it more optional? I found that running around all the time was a little too much busy work.