Most commercial flat roofs installed today are single-ply membranes: TPO, EPDM, or PVC. Each one can give a building decades of service when it's installed well. The differences come down to how the seams are made, how the surface handles heat, and what's on or near your roof.
TPO is the white membrane you see on many newer commercial buildings. Its seams are welded with hot air, which makes them very strong, and the white surface reflects summer heat. For most warehouses, retail buildings, and offices, it's a cost-effective choice.
EPDM is a black rubber membrane with a long track record. It's flexible in cold weather and simple to repair, but its seams are taped or glued rather than welded, so seam workmanship matters even more.
PVC is also heat-welded and holds up especially well to grease, oils, and chemicals, which makes it a strong fit for restaurants and some industrial buildings. It usually costs more than TPO.
Whatever the membrane, the details decide how long the roof lasts: insulation that stays dry, drains that actually drain, and properly flashed curbs and edges. Ask any contractor to explain how they'll handle those, not just which membrane they prefer.