@Andrew Taylor As @Mike V. says, the thing about the smaller units is that there are many more of them on the STR platforms, so there is a lot of competition. But if you have a nice unit that shows well in photos and has good reviews, you'll tend for them to be rented consistently, and if you can have 4 small places consistently rented, I think you'll make more money than 1 large place consistently rented.
But there are so many other factors. For me, my 2 small rentals are in apartment complexes without a lot of maintenance besides HOA and cleaning and utilities, but my nice rental (that gets 3x the nightly rate of the small ones) is a big house with a pool and has very high monthly costs, and more things that break down over time, so my expenses on the big rental are much higher than I would have thought.
So, the problem with my big place are my ongoing expenses are higher than I thought, and the problem with my smaller places is that there is a lot of competition to keep them consistently rented. There is no formula.
You will probably do fine either way, it may be more of what you are comfortable with. If you are self managing, perhaps the 1 bigger place is best so you aren't dealing with multiple guests and check-in / out on the same day. Also check out AirDNA or similar for a 1-month subscription. You can drill into things like by bedroom in a market what is the filled/vs vacancy rate, etc.