I would limit your cardio to 3 20-30 minutes sessions a week for general cardiovascular fitness. Weight training is the best exercise around for modifying body composition. First of all, you build more muscle through weight training. The more muscle you have, the more calories your body burns at rest, since muscle is metabolically active tissue and requires calories to maintain. Also, although you don't burn much fat during a weight training session, you burn alot after it.
Weight training causes increased use of free fatty acids during recovery periods.
My sole activity right now is weight training. Also, look at Richard Simmons. The guy does alot of aerobics, but he ain't that lean. Don't pay too much attention to the scale. The scale can't differentiate between muscle and fat.