People seem to dislike it, and sure at first glance it seems really bad to loose your 6 strongest units for some more biomass on the remaining ones.
But a major aspect of the prestige is that you have an additional 50% chance that the unit drops all of its biomass. Abathurs already gets 50% drop chance at level 7… after that, as long as you pick up all biomass, it will inevitably accumulate, leading to 125 biomass on every single unit.
And that in turn means something like +25% HP, +25% attack speed, +25% energy regen, +25% life leech, etc. Applied to a big enough army, the benefit would outweigh what 6 ultimate evolutions may bring in terms of tankiness and DPS.
I kind of like the prestige… it makes it ok to loose some cheaper units here and there.
I use roaches as a mineral dump and have them tank in front instead of brutalisks. With biomass and upgrades raoches become super tanky too, especiall with the added biomass from the prestige. At 100 biomass they have 580 HP, at 125 biomass they get almost 700 HP. With max upgrades they get 10! armor below 50% HP, meaning they get that for their last 350 HP… that is still a lot.
E.g. they are pretty much immune to stuff that deals less than 15 damage per attack (like zerglings, marines, hydras), pretty much regardless of how many there are.
Fully upgraded marauders with 20+6 damage will take 14 shots to bring them to 50% HP and then another 22 shots to kill one roach… and only if it does not get healed by other units or its own life leech.
Maybe this prestige is weaker than regular abathur with ultimate evolutions, but unless your goal is some sort of speed run, it is not bad at all.