This would be a pretty interesting match up. Arn Anderson is underrated in a lot of ways and is typically only thought of as a tag team wrestler. It's true that, to my knowledge, the only singles title he won over the course of his career were the NWA and WCW World Television Championships, though they were the same title technically speaking. Anderson gave great interviews and had some very entertaining matches.
To me, Ron Simmons was a good worker but he wasn't a great worker. The guy was never all that great on the mic but he was a real powerhouse in the ring. Much of Simmons success, like Anderson, also came in the tag team ranks though he did win the WCW World Heavyweight Championship.
This would be very close in my opinion. Anderson isn't as strong as Simmons, but he's a better overall wrestler. I really don't think Anderson's best move, the spinebuster, would be enough to put Simmons down. I think, in the end, Anderson would take it however with a nice roll up while using the tights or ropes for leverage.
I have to give the slight edge to Anderson. I think that he demonstrated more stability in the long term as a great competitor in the singles ranks than Simmons did.