Any membrane roofing system is only as good as the perimeter and penetration flashings and termination seals so that is what I would be asking about. PVC in a light color should not need to be painted. I'm not fond of open flames on a residential roof.

Thanks for the response. The installer is very good, experienced, and will use a board over the installation, so the decking will not catch fire. I am confident that he will do terminations and seams well. My cheif concern is how a torch down (modified bitumen) roof will work in this type of installation where there could be some small puddles forming (about 1/8 inch deep)?

Renovator, you are correct that PVC would perform better and last longer. However, it is more than twice the price AND most local roofers don't offer it. For the contractos that do offer it, I have no information on their work quality.

I would consider a 1/8" per foot slope to be a dead flat roof so the membrane must be entirely waterproof so it will not leak even if it does not drain and that means no seams (or factory seams) which means the best material is fully adhered EPDM.

Any other membrane should be installed over tapered insulation so the slope is at least 1/4" per foot. You should include in all cost comparisons the probability of having to do it twice. See if the torch down contractor will replace the roofing if it leaks not just patch it.

Do you think TPO will be better than EPDM? and worth an extra 15-20% over EPDM?