Oregen brand has been a trusted name for many years, and their replacement belts are usually an exact fit
"Lifetime warranty" means they are betting that you don't remember when or where you purchased it. LOL It is a selling gimmick most of the time. If you are operating commercial equipment, the warranty is usually not honored any way (Read the fine print).
I recommend you go with what the machine builder suggests. They don't make their own belts anyway; they are outsourced under private label contract in mass quantities from belt manufacturers.
Polyester cord is what most residential mower applications use. Aramid and Kevlar are usually found in commercial mower applications.
I do not recommend any generic "it will fit" online belts due to poor quality issues, so study the source before you buy.