I've tried both methods and I felt stronger with each. However, I felt much, much, much stronger once I started doing the high weight, lower rep type. Additionally, while I would get a slight cardio benefit from using low weights at a faster pace, I was very pleasantly surprised by the increased cardio benefit while trying to move heavier weight, sloooowwwly, with perfect form.
Like most people, my time is limited. So I'd rather get more bang for my buck...I feel that high weight/low rep routines force me to work harder in a less amount of time. Plus, I don't get as bored.
I don't think either way is more "right" than the other...high rep/low weight is great for muscle endurance..high weight/low rep is better for building strength. Both will burn calories and help you become a fitter, healthier you. That said, weight loss is all about calories in vs calories out..and the more lean muscle you have, the more calories you burn at rest. And higher weight/lower rep is better for building muscle.