Better efficiency and longer warrenty doesn't mean it's a better PSU.
But cheaper price does mean it is a better PSU?
Also, warranty length clearly indicates how reliable it is. Since even if manufacturer doesn't believe the PSU to last long, only 3 years, what "better PSU" are you talking about?
Moreover, there are some shady dealings going on with Adata brand of XPG.
This is supposed to be the PSU's official specs: https://www.xpg.com/us/xpg/641
Which is supposed to list 10 years of warranty as well. But i can't access it. I've tried dozens of times now, with different browsers and every time i get "site not found or moved" error.
Though, if you were to go to xpg.com site, and then select XPG -> Official Store, you can navigate yourself to that PSU. Ending up on this link: http://shop.xpg.com/xpg-core-reactor-atx-power-supply-750w-fully-modular/
And on that link, there are no specs. Only wall of text. Oh, warranty is also listed as "3 year limited warranty".
Yeah, all that shady dealings for sure boost the confidence in that PSU, or XPG in general.
Seasonic, in the other hand, doesn't do such trickery. Their website works fine and lists all PSU specs. Link: https://seasonic.com/consumer/power-supplies
When PRIME series first launched, it too came with 10 years of warranty, e.g SSR-650TD (powering my Skylake build). Refresh of the initial PRIME series was PRIME Ultra series, which was renamed to PRIME TX for better understanding to consumers, e.g SSR-650TR (powering my Haswell build). Then PRIME Ultra and now PRIME series PSUs have 12 years of warranty. Seasonic is also confident in their initial PRIME line and they extended the warranty of their initial PRIME units with 2 years as well. Meaning that my PRIME 650 (SSR-650TD) that i bought with 10 years of warranty, now has 12 years of warranty from purchase date.
I have not seen any other PSU OEM/brand to retroactively increase the warranty period of their already produced and sold PSUs. Also, Seasonic is the ONLY ONE that offers 12 years of warranty to their PSUs. <- That is something i trust.