IMO all EPDM liners are equal. They're EPDM. All manufacturers aren't equal, but pretty much are equal for all intents and purposes. Beyond that is just opinion.
I would assume Anjon doesn't actually manufacture the EPDM they sell. My guess it is manufactured by Firestone because Anjon is using the name "LIfeGuard" which is so similar to Firestone's "PondGard" that without being a reseller Firestone would have blocked use of the term. But that's just a guess. It is common for a manufacturer to sell products this way, through rebranding.
Interesting Firestone uses "Gard" rather than "Guard". Bet there's a story behind that.