West System and System Three are heads and shoulders above Devcon or relabeled hobby chain brands (Tower Hobbies, etc).

But the cure times are hours rather than minutes. No such thing as a free lunch.

Hardware store and hobby store are about equal. OK for most modeling uses.

Chandlery and direct from manufacturer are the good stuff. If you are glassing a fuselage or wing - get the real lamiating epoxy and thickeners.

Download the free .pdf Epoxy Book from System Three to learn a LOT about various hardeners and additves that will allow you to get the most out of epoxy. There are ways to lighten, strengthen, speed or slow that most folks are not aware of. If you don't know what "thixotropic" or "milled fiberglass" means you are missing half of the usefulness of epoxy.

https://www.systemthree.com/pages/literature