Just for a bit of context, when PTPP says 'heavy loads' he means HUGE loads. Like 'solar shower on day 14' loads.
I used a protrax for my first few camping walls, including one El Cap route, and it was fine. You definitely want to have the right biner - the petzl locking ovals are optimal. D-shaped biners can lead to shifting the plates, and that way lies deep unhappiness.
The Kong hauler that Pete is such a fan of is definitely the better unit, but it does come with a weight penalty. That said, it's worth it if you're hauling big loads or slabby routes. My protrax is mostly a backup piece since I got my Kong.