I'll second stripes, Crest Whitestrips seem to be the best for me.
I chew Trident White because I like the flavor, I really don't think it whitens my teeth. And I chew with my back teeth, so wouldn't it only whiten those ones? 🙄
I don't know if Trident White actually really whitens, but I get it fairly often because it does a great job of cleaning my teeth, which at least helps a bit to prevent discoloration.
I do not believe that whitening strips damage tooth enamel.
A dentist whitening definitely works best, but hurts like hell and can cost $1000+. I find whitening strips are the next best thing and work quite well. I also brush with whitening toothpaste only and feel this helps. I do chew the gum occasionally but haven't noticed any whitening effects from it.