hmm i'd say xbconnect, because i'm with them, and our mod policy is as follows:
We do not support the illegal portion (ripping, software hacks etc) and what not however hardware mods are a ok, the fact that we dont support the modding scene is due to our current relations with MS.
The forums were removed just basically due to lack of posting, because we have our own separate forums, people posted on there rather than here, so it was merged with GameSpy in the Other Tunnels catagory. Comparison wise, XBC is still one window (i like more) and we have chatters 24/6/365 opposed to xlink with much fewer members chatting, As to games, we cater to mostly Halo players however all other tunnel games work and operate on it fine, just a matter of finding them. We also have live tech support via help chat rooms etc. And indeed as jz stated we have been out longer, GameSpy Arcade is the oldest tunnel program, but due to the ads and what not, people have stepped away into others like XBC and Xlink, Taz has a very good point, just try them all and see what suits you, if you like chatting and gaming, i'd suggest XBC just because we have on average 200 + users chatting at any given time <