Re:
Powder coat is very tough, it took me a lot of effort to sand it off some cheap cranks I bought that had been powder coated yellow, so it will likely last a lot longer than wet paint.
However, it probably comes down to your feet. How much do your heels rub?
If your feet line up with your legs, so, they're parallel when you stand and point straight forward when you walk your heels or ankles don't touch the cranks much. My feet essentially point straight forward and I don't mark my cranks much at all.
If you have feet that turn out, so there's a significant angle between them when you stand or walk, it maybe that your ankles or heels are far more likely to rub the cranks.