Terry is a great organiser, the best I know of in the game right now, by a country mile, Vidic isn't fit to lace his boots in that sense.
Carragher and Terry are big mates, always have been, I wouldn't say him calling Terry "one of the best I've ever seen" means much at all to be honest, but that's just me. And even then he's not really talking about the kind of all-round ability that I was talking about Kompany and Djourou having - Carragher probably thinks of himself as one of the best around, and you wouldn't really describe what he has as real talent.
At Arsenal I think we need the Djourou/Kompany type over Vidic/Terry, in the League in general, where deep defences rule, Vidic/Terry's limitations aren't tested as often.