If you use hot water to shave, Gillette blades dull very quickly. If you use cold water, they last longer than DE blades. It mostly has to do with the plastic coating on the cartridge blades. However, if you're skilled at shaving with a DE, technique actually prolongs your blades life into many shaves with the same razor.
For me, the most noticeable difference is my daughter would never use my DE safety razor on her legs. The cartridge style.. well.. they dulled out way faster than they should have from my usage.
I find this hard to believe. I can use a single Gillette Fusion 5 cartridge for a month or more.