I really like SPWaW and was just playing it the last couple nights. I would love to see some improvements in the graphics (terrain mainly), but I'm am perfectly happy with the game play. I think it remains a great top down UGoIGo tactical wargamer with a surprising amount of detail for a game this old. While, I think CMBN incorporates nearly every feature of SPWaW I like plus great graphics, multiple views, WEGO, etc, I love the huge number of scenarios and campaigns in SP. I know there are many scenarios for CM, but you get tons of scenarios in SP without having to purchase a variety of modules.
I love CM, but I can't imagine managing and moving several battalions of infantry, companies of tanks, AT teams, scouts, transports, Infantry guns, AT guns, etc. like I do with SP. I don't think I have the computing horsepower for that. Not yet anyway. I do think that SP models tank fire exchange and most other fire results better than CM. You can have Shermans blasting away at a Tiger or Panther and the shells will bounce off frequently. CM has way too many one shot kills, I know it happened, but it seems a little too frequent.