For his career, Triple H has created (as in he made someone submit)
2 submission victories. One in November of 2006 against the Legendary (sarcasm) Spirit Squad (5 on 3 handicap match with HBK/Flair, and all 3 good guys locked in Figure 4's). The other submission victory came on September 18, 2002. Triple H was wrestling Jeff Hardy. At this point in time, Triple H was actually using a Sleeper hold on his opponents (usually postmatch). In this contest, he knocked out Jeff Hardy with a Sleeper Hold, forcing the ref to stop the match.
Here's a video of the match with Hardy. The sleeper is locked in at 9:20, and JR brings up how Triple H had been perfecting the hold in recent weeks. While it was the only time he actually ended matches with it, he has used the maneuver, and with some success.
Brock, on the other hand, has created
5 Submission Victories. He submitted the following people: Orlando Jordan, Shannon Moore, Rey Mysterio, Chris Benoit, Hulk Hogan. Yes, Brock had his own submission move (The Brock Lock), but he only ended matches with it against smaller combatants Jordan, More, Mysterio, and Benoit. And the only opponents who really meant much of anything at the time of defeat was Hogan and Benoit (Mysterio was still just a Cruiserweight at the time of their match).
So neither man is really a submission expert. However, there is one advantage Triple H has here (as has been previously stated). The Brock Lock is not a submission that will work on a guy of Triple H's size. The Sleeper Hold, however, will work on anyone (as would the Figure Four and Crossface, which Lesnar tapped out to before). Yes, Brock once used a Bear Hug, but I do not recall seeing him EVER use the hold again.
I'm voting for Triple H here. Yeah, I might be letting my fandom get in the way here, but this isn't as clear cut in favor of Brock as people are letting on. Brock used the Brock Lock on occasion (3 of his submission victories were from December 2003-January 2004, before he lost the belt to Guerrero, and went into a feud with a guy he couldn't get the hold on in Goldberg). It's not like he's a great submission guy of all time here. Triple H has 2 less submission victories, but has more ways to submit him, and Triple H is a much more cerebral wrestler, and will use that to his advantage to work on a body part, before locking on a hold and winning the match.