I've heard some complain about the noise from them mounted on frame. I don't think I'd care but

At least on frame it's away from heat of engine. Didn't go well for me mounted in engine compartment and I'm sure heat played a factor but quality of pump may have as well. My opinion is if there's a tank available for you application that you can submerse the pump in that's best and worth it but at least a quality pump away from engine is good if you don't mind the noise.