If we had a choice between trading for KG or Kobe, I would have to take KG. I'm not saying because I think KG is the better player or whatever, but on the basis that the one thing that could help this team more than anything is having talented big men, and KG is about as talented as they come.
He does so much on the floor from the PF spot, that I don't know why anyone would rather have Kobe. To me, Garnett is a much better "fit" than Bryant, although I do feel that Kobe and the Suns could make it work. KG doesn't bring years of baggage with him either. He's not a player who is going to take questionable shots, or dominate the ball too much, both things that make the Suns offense what it is.
The biggest reason why I want him here though is post defense. He has a history of playing Tim Duncan well on both ends of the floor. He free's up Amare to do what he does best, and that's help defense, and keeps him out of foul trouble.
To me it's a no brainer.