We Terran all love our marine from SC 1 till now !
Even send countless of them to their death (Raynor in a nutshell)
But with the expanding lore, i would like to ask that:
Which is the best marine in the Koprulu sector ?
If you go by game stats then it’s probably warpigs. But if you go by lore it would probably be Umojan since they are well equipped in terms of gear. Though you could argue that dominion special forces are also the same.
If we aren’t worried about marnie count it would have to be covert marines winning in every way.
But if we do account for marine count, it’s a bit more fuzzy. To be honest, probably the basic marines. Because there are a lot of them.
If you can’t win by force, you can win by mass, Russian style 
It’s not question canonically in terms of the entire army, it’s the Dominion Marine Corps. By far they have the biggest military infrastructure.
The only thing that could maybe contest them is the UED’s forces, but it’s unclear exactly what manpower they have, we can presume they’re probably much more high tech than the sector though. But you also mentioned “in the Koprulu Sector” so the UED doesn’t qualify.
For each individual marine it’d probably be the Dominion Special Forces, even the Umojans don’t dump a ton into military technology, whereas the Dominion Special Forces are the best of a very militarized nation.
Maybe for each marine, but funnily enough the Umojans are considered to have the weakest military by a large margin, even behind the Kel-Morian Combine.
Dominion Special Forces Marines, which I think are covert ops, right? If not then rip. But the Special Forces Marines have 150 HP and 9 Damage, which is a lot more than just the warpig, with 75, then 85 with shield, and 8 Damage. I have no idea about the Stats of Mira’s Corps or Umojan Protectorate marines.
Alpha Squadron
“I can’t believe this! Alpha Squadron never would’ve left this equipment behind! That’s what I call sloppy!”
What about the Sons of Korhal (Mengsk’s elite Marine guard)? Do they count, too?
There might be some UED marines remaining. The Spartan Company description in WoL says a few pockets survived and implied that basic UED brood war tech is on the same level as the most advanced Koprulu Terran tech as of SC2. Then again the biggest tech difference shown between Terrans and UED was their healing tech. Pre SC1 material (timeline wise to clarify) had local med tech as maybe Star Trek level and the UED brough the med tech that lets you bring a man back from the verge of death from a distance and in a few seconds
They also mind controlled the overmind. Because biology science OP.
Of course, they did also come out with Goliath Range and valkyries. Seems like the UED just had better anti-air than the dominion in general.
To be fair, nova’s marines only have that watery super stim, which granted does heal the marine instead of damage, but it also only boosts speed by 25%, rather than the 50% of regular stim or the 75% of raynor’s stim.
Hm. In terms of lore, probably Warpigs. They’re mercenaries with an insane amount of ground combat experience, and the standard viewpoint seems to follow along the lines of, “Our marines can’t handle the situation? Better call in some Warpigs.”