I've been trying to give BAR a try, but outside of the Chicken mode(Raptors), or alternate robots(Scavangers) there's not really much interesting for me at least to play over zero-k.
BAR at least look well polished which I've been told puts some people off of Zero-K, from BAR unit graphics being mostly similar to 0K but the default settings making them look better.
The sound design is also better balanced out between various things and they got an easy to use music selection and library, I still get itchy ears from hearing packs of scythes hit things suddenly or snitches chain exploding.
Explosion visuals are better in Zero-K though at least, I barely ever know what just exploded in BAR if it's not a nuke and I still only notice those because there's a voice warning and a slow missile to track as it goes. Sound however is better fitting in BAR than in Zero-K - there's at least to me - far greater discord/discrepancy of sounds between explosion in Zero-K than in BAR.
Which is both a plus and a minus, in BAR explosions to me sound like they're all the same audio file only toned down or up depending on the size that it should be and they don't overlap into ear-pain if someone's base ends up chain-exploding. In Zero-K the explosions are far easier to distinguish/recognize for me even though they tend to 'boom' if there's more than one.
The previous snitch mention is an example, it has a distinct and good explosion until there's a pack of them blowing up at once, meanwhile Singularity Generator also has a good explosion both in sound and visual design, and if several chain explode it doesn't become overwhelming.
Other than that I can only mention personal likes and dislikes.
BAR has rather annoying and convoluted tech-tree compared to Zero-K even without the Armada/Cortex factions being slightly asymmetrical.
Like some faction units are straight up simply BETTER than the other with no drawbacks.
BAR commander's are plain and mainly worth as victory point objectives - There is a custom setting to allow leveling or have changes but still nothing like Zero-K or Future Wars mod. Commander D-gun however does work nice as kill-anything switch.
BAR has functional unit Rank/XP system, while Zero-K has it as a mostly cosmetic thing? - Not sure about this part on Zero-K side.
BAR has wall unit, Zero-K does not. Either add the low + high walls as structures or let something like Solar Generators morph into a generic wall unit since they have a decently big footprint.
BAR has mines, yes I know wolverine exists and snitch/roach/imp cloaks when stationary but I mean build-able permanent mines, light, medium or heavy/large, which is a bit redundant if Zero-K would have them as well.
BAR has rather annoying and convoluted construction mechanics. Units cost metal AND energy to build as separate values. Construction/Build Power is half-false as a statistic because there's also a hidden build-time mechanic? - Zero-K just flat out does this better, so so so much better like damn.
This also ties into reclaim/revive, reclaiming in BAR is very fast because units have a bloated Build Power stat that only ever truly works at 100% when reclaiming, which makes battlefield salvage a pretty fast action. A pack of 5-10 reclaim units can clear out a battle-zone in seconds.
Zero-K does reclaim better as well, it's fast but not too fast and reclaimers are generally easy to punish mid-process, in BAR you either get to kill them before they get to the wrecks or as they're leaving.
BAR does revive slightly better only because it's less of a time waster, if Zero-K got a 2x or maybe even 3x BP boost to reviving it would be at a decently fast pace but not too fast as BAR is.
In BAR you can get reviving units at the 1st minute of the gameplay if you rush it, in Zero-K you either build Athena which requires Strider Hub or morph rush the Economy commander with Lazarus module which is a little bit too late if you ever had intention of reviving early-game units.
Alternatively adopt Future War's caretaker upgrade.
BAR doesn't have factory plop token's at the start of the match, Zero-K does and it skips the annoying build-up aspect of most RTS games I've played. Some games have it longer, some have it shorter but Zero-K's way is as far as I'm concerned the future of the genre.
BAR has unit counter/bonus modifiers which boggles the mind, Zero-K does it simple and better. Damage is damage.
BAR air units don't leave wrecks/corpses which is just weird. Air balance is also weird to use, like Planetary Annihilation's air, if you start with constructor and enemy with a fighter you're not going anywhere and you've lost the game.
Bombers also don't need to re-arm, Zero-K air works better either gunships or airplanes.
BAR doesn't have shields(has plasma deflectors[can be made into proper shields via lobby settings]) or proper cloak units, but it does have the Juno anti-intelligence structure which Zero-K could use something like that. Could work wonders with the supposed cloak/Cornea problem.
BAR anti-nukes have to build-up ammo as well to shut down nukes, this feels like a good difference compared to Zero-K but I don't know how the difference in BAR tac-nuke silo and Zero-K missile silo would work as BAR only has tac-nukes while Zero-K has several types of missiles for the silo.
BAR has the absolutely annoying mechanic where some units die differently if you kill them via Self-Destruction, infuriating to look at let alone try to memorize between units. Zero-K does it best like it does with damage, death is death. BUT, BAR does show count-down on the self-destruction which could be added to Zero-K, or if it has then for it to be made default setting.
BAR has too many defensive structures, and I say this as a stubborn porc player. Variety is nice, but there's just so much extra stuff that seems entirely redundant.
AND THIS IS WITHOUT EACH DEFENSIVE STRUCTURE BEING DIFFERENT BETWEEN FACTIONS!
Compared to Zero-K the only thing BAR does better in the defense side of things is light defenses can be transported around and there's porc+ versions that Scavanger faction/AI can make that you can also enable as always buildable by everyone in the lobby settings.
BAR doesn't have terraforming, Zero-K does. That's a thing for our side as well.
There is map deformation and technically terraforming through that with only "Restore" option to un-crap the map if it's gone too much, but from what I've experienced only nukes do any significant amount of terrain deformation to matter.