From what I've read, Tonalin is the one that has the most studies backing it up. I can't really speak to the difference between the two, as I've only been taking CLA for a month now, and I've only had Tonalin, but from all my research everything pointed to using Tonalin, which is made from Safflower, not Sunflower oil.
MRM's CLA 1250, for example, isn't listed as Tonalin, but it's the same thing, since it's made only from Safflower oil. I believe "Tonalin" is just a trademark name...
Hopefully someone else can tell you more about results!
"If you saw two guys named Hambone and Flippy, which one would you think liked dolphins the most? I'd say Flippy, wouldn't you? You'd be wrong, though. It's Hambone." - Jack Handy