I was in this situation a month or 2 ago. I considered doing HIDs in some Hellas but decided to go with the PIAA 520 ATP. Ultimately, for me, it came down to the fact that none of my other lighting has been converted to HID (and no plans to currently) and I already have PIAA bulbs in my headlights and fog lights that match. The PIAAs can be converted to HID down the road if I do my other lighting, but I doubt I will bc these PIAAs are really bright and fulfill my needs very well. I wanted them to throw light down the road and light up the sides to see deer on backroads before it's too late.
Another HUGE plus for the PIAAs is the wiring harness. The install was crazy easy bc the harness is already pre-assembled and just needs to be connected to the battery, wire tapped, and plugged in.