Energy density is the word you're looking for. It's a important metric for many application (smartphones, EV, etc.) but not for everything: for instance when it

Energy density is the word you're looking for. It's a important metric for many application (smartphones, EV, etc.) but not for everything: for instance when it comes to grid storage, the TCO trumps everything. And even on cost it doesn't necessarily make sense to compare innovations against the incubant, because lithium-based battery have had lots of R&D over several decades to make them “cheap”, and it's impossible to know in advance who's gonna win in the end: innovation necessarily involves multiple failures for every success.