low weight & high reps vs. high weight low reps

I would suggest doing some research on your own. Just google. This site and its users can sometimes be of great help, but it can also steer you in a terrible direction. Dont get me wrong, I have learned a LOT from the people on here. The problem with asking a general question like this to a bunch of people that are probably telling you what they've only heard from some other unknowlegable source is you are going to get a lot of back and forth and incorrect info mixed in with the good stuff. It makes it hard sometimes to decipher what is good and bad.

I mostly lift pretty heavy because I like it, and I am trying to get stonger along with improving my physique, but I also still do cardio and lower weight training. Circuit training with lighter weights is a great strength/cardio workout, and I like to mix those in every once in a while too. I sweat more during because of the fast pace, but I burn just as many calories lifting heavy and taking longer breaks.

I think it's good to mix it up. Try them all see what you like best. You can find an infinite number of programs and routines online for free. Just be careful with lifting if you are just starting out. Be sure to learn proper form on the lifts.

Regardless of what you choose to do with your lifting endevours....if you are working hard at it, mixing in cardio a couple times a week, and eating at a defecit....your body will transform. My overall point is to lift weights for sure. It's good for you. Also to read reliable sources about the differences and lifts before you start. The peope that lift heavy will tell you that its the gospel, and the people that don't will say it's not. The truth is that they both work. It's science and balance of each is key in my opinion.

This article addresses a few studies on the issue. http://www.danogborn.com/training/30/

This is a REALLY great read!