Gaining more muscle which will lead to the ability to gain more strength, in the long run.
Slow twitch muscles may benefit more from higher reps than fast twitch, but I generally stick to lifting heavy.
I did something like 2-3 months of doing all my lifts 3x12 with some cardio and eating healthy, and I believe I lost around 10lb, but I didn't look "jacked". I then gained the weight back after I got a knee injury.
Fast forward to now, I am on week 11 of doing MAX OT (which is heavy lifting, google it if you want) and I am down around 2-3lb, all fat. I look more "jacked" than I did 10lbs ago, because I likely lost muscle doing the 3x12 because I wasn't pushing myself. When I lift heavy, I feel maxed out (no pun) after I lift. After a 3x12 I was just filled with lactic acid and I didn't maintain my muscles, especially because I did cardio right after. Currently, I am not doing cardio..Just sports 2-3x times a week. I am now hitting the gym 2x a day, with a heavy lift around noon, and a quick interval session around 4:30-5pm. On days I have hockey, I'll skip the 2nd session.