TPO or EPDM for a 900 sq. ft. low-slope roof with occasional ponding?

I’m comparing TPO and EPDM for a small low-slope roof, roughly 900 square feet at about 1/4:12. It gets strong summer sun, has some occasional ponding after heavy rain, and there’s an HVAC unit that requires periodic service, so this isn’t a no-traffic roof. I’m planning walkway pads around the service path rather than allowing unrestricted foot traffic.

The appeal of TPO is the heat-welded seams and reflective surface. Properly welded seams seem like a strong advantage where water may stand temporarily, and the lighter surface could reduce heat gain. My concern is that seam quality, welding conditions, substrate preparation, and installer skill create more variables. Repairs also appear less straightforward if the membrane gets damaged later.

EPDM seems simpler to detail around penetrations and easier to patch with compatible primer, tape, or flashing materials. That repairability matters on a roof with occasional HVAC access. On the other hand, I’m unsure how much the darker membrane would affect heat exposure and whether taped seams and flashing details are as forgiving around ponding areas over the long term.

For a roof this size, would you favor:

- TPO for welded seams and solar reflectivity, provided the installer has strong membrane-welding experience?
- EPDM for simpler detailing and easier future repairs, with careful attention to drainage and walkway protection?

I’m more interested in lifecycle risk than brand reputation. Which details would you inspect most closely in the proposal, especially around drains or scuppers, HVAC curbs, perimeter edge metal, walkway pads, and the manufacturer’s ponding-water and workmanship warranty language?