The main advantage the Jem'Hadar have as far as fighting goes seems to be their ability to endure pretty much any privation indefinitely, save lack of White, their (so far perfect) cloaking, and their training. The former would be a huge advantage in any drawn-out battle, the middle perfect for ambushes, or at least getting into superior positions, and the last when it actually came down to getting it done.
The Hirogen could meet or exceed them on the latter (heck, Worf did
), and can almost definitely beat them in strength. Don't know about detecting them cloaked, but they figured out 8472 camo when Voyager couldn't (and don't they have a cloak of their own?)
One-on-one I'd say the Hirogen wins, but in a group the Jem'Hedar do, as that's more their speed.
Vs Data...that depends. It seems most of Data's combat limitations that we've seen are of his choosing. I don't think we've ever seen him do much close to what he's said to be capable of.