Which level 1 creature is better?

No, if the halberdier strikes first, there's no chance, but otherwise, the Captain will defeat everyone without any problems, even fairies, one hit and they're gone – I'm talking about the fairies.

Well, firstly, the fairies will strike first, and secondly, if you're lucky with the terrain, the centaurs might not even get to attack at all!!! Although this is more of an exception... of course, if the centaur captains attack, there will be very few fairies left (if any remain).
However, when I was talking about fairies, I meant that at the beginning, they can do some serious things!!!
An example from a real game: Random map, Conflux, near the castle there are Angel Wings, which are guarded by about 100 (I don't remember exactly) gold golems. Theoretically, they can be defeated by fairies! And what can you do, having Angel Wings at the beginning... it's quite something!
If we talk more realistically, then it's easy to capture mines, for example, guarded by a large number of slow monsters. This happens very often.