Are treadmills and ellipticals really worthess for losing weight?

so i want to lose fat and build lean muscle. i told my fiance(ex military mind you) that i wanted either an elliptical or treadmill for my cardio. he basically told me they're both worthless for what i want. he told me i should look at a set of resistance bands with varying resistance to build lean muscle and something hard like plyometrics(p90x) for cardio. i haven't worked out in a long time and feel like p90x would be too much to start. what do you guys think?