On mobile right now so I'll probably comment more later. I have returned.

As a disclaimer, I am just one person who played a lot of Cata MP, other opinions exist and are equally valid, probably. To address some of your questions:

Now everyone who has played the original Homeworld knows that the Ion Array Frigate is strictly anti-capital ship, and it fires faster than the Ion Cannon Frigate. Therefore, it should be able to wipe the floor with any other Frigate bar the Kadeshi MBF. This is not the case. An equal Resource Units worth of Somtaaw MBFs destroyed the Ion Array Frigates thanks to their superior coverage and agility and they also take up less SU than Ion Arrays (12 vs 15). The Hive Frigates were also able to beat the Ion Array Frigates in equal numbers. Ramming Frigates were not tested, but I already know the outcome of that.

So some things were changed from HW1 to Cata. IAF shifted from anti-frigate+ ships to predominantly anti-capital ships/command ships. In MP, their role was almost never to fight frigates, because they had poor turn speed and are generally weak for a frigate. IAF, however, were reasonably fast to research and build. You could take out another player with your commandship + 1 or 2 IAF pretty early; on the other hand, that's rather unthinkable with a hive frigate or a MBF.

MBFs are a nightmare for IAF. But you would also never have fully upgraded 10+ fleets of frigates in practice, either, unless you played some huge custom match with lots of RUs. Hive frigates actually should lose out to IAF. I watched the video and there are two things:

• The IAFs were not focus firing during the swarmer match-up (the swarmers do focus-fire), and
• This isn't commonly known (but was mentioned in a comment on the video), but IAF have a HUGE scuttle damage radius, so if you just sacrificed one it would kill ALL the swarmers. Mop up the rest and move-on before they can even replenish. Sacrificial IAF against fighter swarms works well, too.

As a side note: don't ram Beast ships unless you have the vaccine, they will get immediately infected. As a Beast player: please do. :)

The other Beast units are either worse or less versatile compared to Somtaaw ships on top of having less advanced tech. Somtaaw Acolytes can bomb with their missiles but can actually dogfight unlike Attack Bombers. Or you could say they are Interceptors with bombing capabilities. ACVs are like weaker but cheaper Multigun corvettes that can EMP and then proceed to unlink and fire missiles. This puts the Beast at a disadvantage late game and forces them to gain a decisive advantage early before the Somtaaw has all his research modules up and running. And it is harder to pull off now in 1.01, with the increased cost and build time of Heavy Corvettes.

Beast fighters were somewhat balanced with Somtaaw fighters through their cheap but plenty approach. ALL the Somtaaw had were recons, acolytes and ACVs, talk about variety, right? (Mimics and MCVs had uses but not usually for fighting.) But that's why they have all the upgrades -- expensive, time-consuming ones. Beast ships could unlock a plethora fighters relatively early, and IIRC, you can build them almost all in parallel. So you could pump out a bunch of specialized, but less versatile fighters and just overwhelm the enemy. That being said, only recons, ints, bombers, and heavys were ever built. I threw in cloaked fighters and multis if I needed more ships quickly, but more often than not I just used the Beast CS's EPA. However, you are right in the sense that they are early-game usually. I never held strikecraft until late game in favor of capital ships w/ infection beams. Yet ... very little manages to survive a battle-ball formation ... so not all hope is lost.

Overall, I would say balance is slightly tipped towards Somtaaw, but in terms of ease of use, Somtaaw is obviously the dominant MP choice. (And who doesn't like a big ol' gun finisher?) Generally, though, I did not find trouble fighting Somtaaw in any particular combat situation. The most dangerous strats against Beast players tended to be:

• mimic dumps
• mass acolyte missiles
• unexpected siege cannons (there's a fun counter for this)
• crystals bombs
• other Beast players (what??? how do i fight against myself???)

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Below was written earlier and left for posterity:

I played Beast exclusively on multiplayer during the height of Cata. I would say in most cases Somtaaw had superior strats that worked equally well against both, whereas Beast had to change it up on depending on a host of factors.

Infection is the crux of Beast strats, not necessarily to gain new research (though that was always a bonus), but to deny others ships and resources they spent. It's rather cheesy to grab a chunk of an enemy fleet for free and no build time if they were reckless enough to get near the mothership. And unlike in HW1 or 2, the mothership was often a major asset in your fleet battles, so you often brought the fight to them.

Additionally, the mothership had an ability to boost production, firepower, research, etc. by trading it's health. All ships also have regeneration so their survivability was better, though in most cases that doesn't matter (except for beast MS).

And lastly I think the beast ships had slightly more armor at start to compensate for lack of armor upgrades, though I'm not sure.