I usually buy the Guitarist, but lately they've gone down the Jazz/Blues/Acoustic route so much, there's less and less of interest in it for me.
American Guitar World on the other hand and Total Guitar are probably too much metal-orientated. I sometimes buy them if there is a song/workshop/article I really want. There rarely is.
German Gitarre&Bass is a notch up in quality, and also a bit thicker (hence there's more variety). Unfortunately, I really only can get it when I pass through the Airport in Frankfurt.