I did some digging and, incredibly, it would appear that Rey Mysterio and Chris Benoit only ever had one singles match together. These guys were contemporaries in a pretty strict sense of the word but - as far as recorded matches that end up in The Big Wrestling Ledger of Wins & Losses go - they only ever had a single one-on-one match together. October 3rd 2002, SmackDown, in the main event. Oh, and Rey Mysterio won. It was considered an upset at the time. Big picture, I wouldn't say it was.
In terms of kayfabe success, it's actually difficult to separate the two - they're on a very similar tier. Midcarders, upper midcarders, sometime main eventers. A trophy cabinet heaving with intercontinental and tag team belts, with only a smattering of world championships. In Benoit's case, his WCW World Heavyweight Championship, which he vacated the next day, and his four month reign with the World Heavyweight Championship. In Mysterio's case, his two World Heavyweight Championships and his WWE Championship, which he lost to that usurping prick John Cena the same night.
Personal preference - I'm going with Mysterio all day long. Benoit, I'd say, was an overachieving midcarder, whereas Mysterio - since 2006 at least - has been an underachieving main eventer. Splitting hairs perhaps, but one I'm prepared to split. The whole dead family thing aside, I'll confess to having liked Benoit and liked his matches. He had a tenacity and rawness to his performances that I found fun to watch. Mysterio is on the other end of the spectrum - smooth, flawless and breathlessly organised; a man in a mask who does flips and who's a king of psychology.
Their match history together - their singles match history together - is one match in which I don't think either were in their primes, though Benoit was possibly closer to his. In terms of success, their title records aren't entirely differently, though I'd say Mysterio has had more longevity - if only because he hasn't, you know, killed himself. Hey, still counts. Who made me care about them more? Despite some misplaced resistance, Mysterio.
Mysterio, deservedly, by a nose.
Edit:
I just found the match on YouTube. Let's watch it together:
[youtube]TIIFn4DjPkM[/youtube]
[youtube]YL9mYK9lojE[/youtube]