I suppose a lot of this (attachment method) comes down to personal preference, experience and skill set. Personally (my preference) I l've always just drilled holes. As long as you do that properly, there is no chance of water intrusion. Or, at least, in the three decades that I've been doing it that way, everything has been OK (knocking on wood).
I will say that I'm a little leary of a "peel-n-stick" solution for long-term - but that's just me. The HDPE/5200 solution I would imagine is a little more sturdy, even though 5200 doesn't stick extremely well to HDPE. But drilling blind holes in the backside of the HDPE can provide more surface area for adhesion, as well with adding to the mechanical adhesion as opposed to just chemical.