DAMN! This is a tough one!! Both are amongst my favorites over the years.
William Regal is one of the greatest technical wrestlers ever. No doubt. He's also VERY underrated on the mic. He's have made a fantastic world champion, and it's such a shame he was never given that chance. Now, he's moved into commentary and is the GM of NXT, and he's doing a great job in both departments. His commentary is one of the things that makes NXT good, and he can still go in the ring if needed.
Booker T, well, he's the 5 time, 5 time, 5 time, 5 time, 5 time WCW champion, and 1 time World Champion in WWE too. Arguably, he's the most successful guy that made the jump from WCW to WWE. He can also still go and is in fantastic shape for a 46 year old guy, shame that WWE don't use him as a full time wrestler really, as they could really use some experience on the roster. He's also made the jump to the commentary like Regal, and while not as "good", he adds a whole new dimension and meaning to commentating, and is funny as hell!!
I really can't decide, and in the end I've had to flip a coin, as I'm happy to see either guy go through.
Booker T wins DAWG! Now can you dig that? SUCKAAAAAAAAAAA!!