I don't have answer for you, but Alec over at Technology Connections made a video few days ago related to the topic. That might not have the answer for you either, but as his videos (and there's a ton of those, even for refridgerators) are among of the best at youtube that is worth cheking out.
But as a rule of thumb, new materials and hardware are better on pretty much every metric. And if your current one doesn't work properly anymore it'll most likely uses way more power than it should, as coolant flow/insulation/something isn't in fully working condition and thus compressor needs to run more often than on a new unit.
I have older 1500VA FSP UPS, I don't think that exact model is available anymore, but it's been solid for several years. It currently has 3rd or 4th set of batteries and they are standard bulk batteries, so replacements are easy to find from anywhere. Only problem I've had with that is that on display it doesn't give out clear warnings when batteries degrade and it has crashed my system few times in a power outage, but I've been lazy and didn't bother to properly monitor it nor have scheduled battery replacements, so that's mostly on me.
Eaton seems to be pretty solid too, but I don't have a ton of experience on any of their models. Local suppliers had dirt cheap PowerWalker UPS's a few years ago, but one of them didn't survive when battery died, so maybe I got what I paid for. Those worked fine too, but apparently they cooked the carging circuit when battery degraded.
This is of course just my own experience over a few models, but personally I wouldn't spend my money on APC. Propietary batteries and multiple failures after battery replacement at work few years back were enough to choose something else.