I love Delirious.
He's the only guy in the whole of Ring of Honour who I'll confess to being a fan of. He puts so much effort and creativity into his gimmick, even is he's just performing in front of three dozen people in a basement somewhere.
His charicter is fresh, funny, and memorable; whilst at the same time doesn't get in the way of his in ring ability. Which is passable. I'm not overly sold on his matches, but the character is enough to prevent me from changing channel.
That being said, DDP is another on of my old favourites. He was innovative, entertaining and remarkably solid inside the ring. He was the kind of ring technician that I liked, in that he worked something of a technical style, but didn't over blow it to the point of looking like a farce.
The Diamond Cutter should also go down as one of the best finishers in wrestling history. Most finishers get over souley based on who it is using them (There is nothing special about a stunner or a tombstone), the Diamond Cutter in contrast got over based on how it was used. "Being able to come out of nowhere" is a line the announcers feed us constantly, which is hardly ever true. Orton doesn't hit the RKO out of nowhere, he hits it under very consistant circumstances.
DDP really could finish a match at any point. I've seen him pull a cutter out as a logical country to dozens of different moves. He's transferred into it from a fireman's carry, an inverted face lock, a power bomb and many other holds.
I like both guys, but I'm going with DDP here.