they have some other advantages, like offense and defense bonuses that only apply to certain types of matchups. but those advantages are usually negated because every barracks unit has more health
Baisicly what you're saying is... No point to upgrade residences past level 15, since level 15 residences gives population too.
You are very close to discover the true power of MC units.
When you compere health, please consider those bonuses (defense & attack).
You really should do some auto fighting to understand that there is not only basic unit stats, there are these advantages: offense & defense bonuses, range, movement, doing first hit to enemy & applying spells instead of receiving hit first and getting spells on yourself, when to focus fire enemy squad or when spread first hits to cripple all enemy squads.
And production speed is up to you, since you want to have your MC units at mid/end of chpt. 11.
But to get decent training speed at that point, you want to start working on your FA asap (end of chapter 9).
MC units are a LOT BETTER vs barrack units, if you know how to use them that is. That's a fact. (next tier units)
Its up to you, how fast you produce them. No excuses ....
The correct question here is do your play style requires this effort.
There are players who compete for top spots in tourneys, there are players who compete for 30th place in tourneys.
There are also players who compete for top100 and there are players who don't compete at all.