Most I've seen are 4-strokes - saving fuel is important; and so is reducing mechanical problems. They can get a lot more hard hours out of those 4-strokes than with 2-strokers.
Even down in Loreto now, 4-strokers are out-numbering the 2-strokes by a considerable margin. I did see a lot of old Mercs on some skiffs but all the guides who can afford one, are going with Yamaha or some other top 4-stroke.
In Australia, it's Yamaha, Honda or Suzuki; but there are always noted exceptions.