EPDM, particlalry if you can get either a single piece or a factory seamed piece to cover the entire roof. There should be zero holes in an EPDM roof.
Modified Bitumen is much thinner and does not last as long.
If you want to try the job yourself 'flat roof solutions' sells cut sheets in a number of sozes and has everything you need.

Depends on the type of modified bitumin roof.

Self adhesive or heat welded modified bitumin membrane can cost far less than EDPM membranes and do not need certified installers to place them.

Self adhesive modified bitumin is definitiely a DIY project.

EDPM requires certification for any warranties to be extended, and EDPM roofs are not warranted by manufacturers for residential application.

Your roof warranty is only as good as the warranty your certified installer gives you with an EDPM roof, if any.

My preference is for self-adhereing modified bitumin roofing.

Easier to install than EDPM and easier on the wallet and it does come with a warranty.

Either way is waterproof.
If you want color, MB is the best choice. It comes in many attractive roofing colors. EPDM is usually black or white.

EPDM is .045 or .060. Most MB's are 4 MM thick. Both products can be fully adhered. MB offers a self adhering product which is very popular among roofing contractors.

EPDM is more specialized. It needs proper cleaning agents (primer/cleaner) along with proper sealing caulks (neoprene) and the specified adhesive (water based or solvent). Shortcuts are common among EPDM installers which result in early failure.

Michael

Roof warranties are not exactly very useful. None of them cover labor anymore, just material. The installer is left to issue any other warranty covering the labor (good luck).
EPDM is the last roof that really needs a warranty anyway. If installed correctly the stuff lasts so long early installations have yet to fail.
This is one of those things were you get what you pay for. I have installed a number of EPDM roofs over the last 30+ years in residential, and have yet to have a problem with any of them.

Great info guys!! With this added knowledge I'm much better equipped to ask more educated questions to these contractors. Thanks a lot.

Installers who do EPDM correctly have been hard to find, based on my experience. But done correctly the EPDM would be my choice. Wind and petroleum oils/solvents are the main enemies of EPDM.

Roof warranties are not exactly very useful. None of them cover labor anymore, just material. The installer is left to issue any other warranty covering the labor (good luck).

That's not true. Workmanship warranties have been around for at least 5 years. GAF and Certainteed offer very good labor warranties when the work is performed by a roofer certified by either company.

If you wish to study EPDM installations, go here:
http://www.stafastbuilding.com/roofingproducts/installation.html#

Michael

Here is a link that might be useful: Warranties & Guarantees

Companies like GAF might claim warranties for their products and installations, but just try to collect on a failed product or installation.

GAF is so bad in backing up their products, I won't ever use their products anymore and tell all my customers to avoid GAF like the plague.

Can't believe they'd back up labor for their installations when they don't back up their products in reality.

Hmmmmmmmmmmmmmmmmm....strange behavior there.

Why not examine the warranties before claiming that they don't offer or honor them?

Don't mislead your customers. Get the facts!

Michael

I have gotten all the "facts" I need by the shabby treatment from GAF through the years relating to warranty claims.

GAF will balk and stonewall and blame everyone and anyone but themselves for defective products.

I'll never use nor recommend their products to anyone.

Thanks for that link Michael_H.