There used to be a dyno sheet on RPS that showed you actually lose power with the JET chip. I'll try and find it. Personlally I stay away from JET all together.
As far as superchips, It might make an improvement, but there seem to be many more ranger specific tunes with something like an sct x-cal. If you have a local tuner, that suggests using superchips, and can tune the truck for you in person, then I say go for it. But if you're doing mail order, I'd go with an established tuner like Fred @ rogueperformance. He's an SCT dealer, and has tons of 3.0 specific knowledge. He can account for any other mods you may have, so that you get the most out of your tuner.