Armada Loot is divided based on ship power (not including the chest for launching, or the random chest awarded).
This means if you need a couple of bigs to carry you through an armada, you’re likely getting less loot than if you were raiding with 4-5 other ships of similar power. The loot increase from a 35 Uncommon Exchange to a 37 is about 50%, same with the rough power needed.
This also means it’s not a good idea for very small ships to join huge armadas. Here’s some numbers:
Exchange 40 uncommon has around 2900 loot. A 700k Stella being carried by 6M of other ships is going to get around 290 loots, and likely a free ride home. 5 ships at 700k can farm level 35 Uncommon, and get around 260 loots. Other than the 2 chests, and depending on your loot multiplier, you might be better off with similar-powered ships against a more reasonable armada target.
Note – these numbers don’t include the loot bonuses from the level of the Stella, crew, research, artifacts, etc.
Note – the starter chests are big, so if you can find 1-2 people that can solo an armada and are willing to carry you, jump all over that opportunity.