Hands down, I would get a pearl gourami! Beautiful & peaceful. If you really want more than 1 gourami, get 1 male & 2 or 3 females. DO NOT get balloon fish of these or any other fish. Not only are they hideous to me, they will be very short lived because of this inbred deformity.
Dwarf are prone to an iridovirus & are pretty pugnacious for their size.
Blue gouramis (or the color varieties gold, platinum etc) are semi-aggressive. I bet 1 would beat the snot out of smaller dwarf or more peaceful pearls as adults. Females are often a bit less aggressive but not mellow.