There are LOTS of kinds of epoxy products. For the resin, it can be bisphenol A, bisphenol F, or Novolac (modified bis-F). For the hardener, there are many chemicals, but the classes of chemicals are aliphatic amines, polyamides, cycloaliphatic amines, amidoamines, and aromatic amines.
Polyaspartic polyureas are not as chemically diverse as epoxies. A polyaspartic is going to be a better product than most of the typical "garage" epoxies.
Are there epoxies that are better than a polyaspartic? Well, that depends on the application. For example, a Novolac epoxy will have better chemical resistance than a polyaspartic. However, Novolacs are fairly brittle and may not be the best choice for the application.
You can buy water-based epoxy which is basically the bottom of the barrel as far as epoxies go and no doubt it will be inexpensive. You get what you pay for.