At the end of the day, it's all calories in vs calories out that will determine whether or not you lose weight. There are pros and cons to different rep ranges when working on weight loss, but that's really not the area to spend most of your worries on.
Supposedly, a 1RM clean and jerk can burn 14+kcal. Given the amount of movement in a C+J, and the likelihood that this number was taken from a heavyweight male lifter, let's dial the numbers back a bit for a more likely exercise to be performing, the squat, and say that it only burns 5kcal for a 1RM. Assuming all other variables of the exercise remain the same (not a good assumption to make, btw), a single squat at 50%1RM would burn 2.5kcal, but you could do it much more than twice...you could do that 20 or more times, for 50kcal or more, and that's per set. What I'm hinting at here is that the lower the %1RM, the less calories youu're likely to burn per rep, however the more reps you can perform, burning more total calories. This is part of the reason why cardio is effective for burning calories -- running a single stride won't burn much energy, however running 10,000 strides will multiply that tiny amount of energy burned by 10,000.
So, if choosing between 10 rep sets and 15 rep sets, the 15 rep sets will probably burn a little more energy than the 10 rep sets, which obviously has it's benefits for weight loss.
However, there's another side to fat loss, other than the calorie balance equation, and that's making your body prioritise what tissues to keep and what to get rid of. Obviously, your body's going to hold onto the brain, smooth muscle and cardiac muscle as much as possible and for as long as possible, however, what of skeletal muscle? The lower the intensity of the exercise you perform, the less muscle fibres you're likely to stimulate. When you stimulate a muscle fibre, you tell the body: "Hey, I know you don't have enough calories coming in, so you have to get rid of something, but we need this tissue to keep on surviving."
When you lose weight, your body generally culls the least important stuff first, so you need to make your muscle mass valuable, to maximise the amount of fat lost per kilo of bodyweight lost, and minimise the amount of lean tissue lost. And heavy lifting will do that more reliably than lighter loads will.
I should note that "heavy" is relative to your ability to use good technique. So what's "heavy" for me might be "light" for you, and vice versa. I'll arbitrarily say, to keep it simple, that a "heavy" set of an exercise should be >80%1RM, and your "1RM" (1RM means 1-rep max, btw) should be determined by what you can do with good technique, not the most you can possibly move.
A simple way to do this without thinking too much about it would be to work up to a weight that you can do correctly only for a number of reps that can be counted on one hand, and then back off and do some higher rep work, then do some cardio if you feel so inclined, and above all make sure your nutrition is in check.