Who's the better ally and the better villain?

[2K3]

When it comes to Slash, Leatherhead and even Wingnut, both have had different allegiances over the years. At one point they are the most dangerous "non-human" threat the Turtles have faced; and at another they are the best of allies (heck, all three have been members of the "Mighty Mutanimals" at some point).

So I ask you... if you had to pick, who is better an ally and who is better a villain? (You can chose all if ya want)