I'm about to have both set up, so i'll let you know which i like better.
So far H-Hour is the better game because it is current & modern, but i haven't been able to play a game successfully yet, but i think it is my connection, not the game. All you need for H-Hour is a controller to plug into your PC & buy the game on Steam for $5 & you're all set, so it's easier to get into, BUT with all of that said...
There are 10x as many people playing Xlink, but you have to get a PS2, & the games still so it can be more difficult to get into, but i feel like once you're in the experience is better.. definitely more authentic since it is actual Socom, & not just the maps.