I honestly only played one game using AlterIWnet, but I loved it SO much more then IWnet.
Pros: You have the console, and it's free.
Cons: No friend invite system, no anti-cheat (as if VAC counts. xD), always get paired up with someone across the world. :/
Pros: Friend invite system, some kind of hacker protection (doesn't work very well), a lot more people play.
Cons: Always paired up with a lagger, lots of hackers (unbearable to certain points).
That's really the only things that I think are pros and cons. I still think that AlterIWnet will do better then IWnet because they actually ban hackers.