I could see this match going to either guy. Both of them had a very strong presence in the mid-card and tag team scenes and accomplished a lot in those areas either in Mid-Atlantic/WCW, WWF or both. Valentine was more of a journeyman wrestler for the first 5 or 6 years of his career before heading to Mid-Atlantic and became a major player there. He won the US title 3 times, the Mid-Atlantic Heavyweight & Tag Team Championships twice & once, won the TV title 4 times and the territory's version of the NWA World Tag Team Championship 4 times. Valentine also left his mark in the WWF with an IC and Tag Team title run.
Tully Blanchard spent most of the first decade of his career working in Texas, especially for Southwest Championship Wrestling. Incidentally, it happened to be owned by his father Joe Blanchard and Tully was a major player. As tempting as it is to say it was nepotism, it wasn't the case as Tully had the talent to warrant being pushed. Tully eventually made his way to Mid-Atlantic in late '83 or very early '84 and spent the next 5 or 5.5 years as one of the biggest names in the business. He was a dominant mid-card guy winning the TV title 3 times, National Heavyweight & US titles once each and two runs as NWA World Tag Team Champion with Arn Anderson. Blanchard was also part of the original Four Horsemen when most of his success in the company was going on. He & Anderson eventually went to WWF, had a run with the tag titles, but was fired for testing positive for cocaine. After that, he kinda just faded away.
Valentine's the rougher of the two, the better brawler, stronger and had a lot of stamina. Tully was quicker, more athletic, and always struck me as the sneakier of the two. I'm going with Blanchard because, for me, he was FAR more entertaining and charismatic than Valentine and his legacy as part of the Four Horsemen makes him the bigger star. As I said, I could see this match going either way when it comes right down to the crunch, but I'm backing Tully here.