There are 3 different type of roof systems
1) Screw down roof with ZAC lifetime fasteners
2) ULTRA DECK SNAP LOCK STANDING SEAM
3) STANDING SEAM WITH SEAMER
Screw down 26 gauge PBR panel roof , installed correctly, is least expensive. Screw down roof systems come in either bare galvalume or a variety of colors and last for years if properly taken care of. Most mini storage buildings with screw down roof system come with a ZAC lifetime fastener that penetrate thru the roofing panel and fasten into the purlins and are sealed with mastic tape between the panels and at the eves.
Ultra deck snap lock standing is a type roof systems with no fasteners and is usually as 24 gauge color or galvalume . There is no penetration of fasteners in the system as it is usually snap locked onto the purlins and if cared for properly will last the lift time of the building, is less likely to ever leak but cost is generally double that of screw down system.
Standing seam done with Seamer is the most expensive because of labor to install and rental of seamer generally provided by the metal building supplier.
In summary, all roof systems, for a metal buildings , installed correctly will last the lifetime of the building and have no leaks provided the roof is maintained properly.