I think doing a variety of cardio and strength training is the way to go. It eliminates boredom and does a better job for your body. I've read that if doing the same exercise all the time, your body gets used to it. Still, any exercise is better than none but doing different things would use different muscles.
I disagree with that "it's pointless" statement you were told. For many heavy people, strength training is actually an easier activity to start out with and strengthening muscles will give the body more stamina to then undertake cardio. Plus, for the out of shape person, strength training can give confidence...ever start out exercising with a Zumba class at 304#s? NOT good. And those experiences can discourage people from continuing to exercise further. I say: try a bunch of things, find what you like & do them all (not at once though! LOL)
Congrats on getting up to working out for an hour...that's a huge accomplishment.