User blog comment:Whitehorse24/Who's your favorite?/@comment-26618197-20161208181633

Hmm if you're looking for the one that can resist plenty and hit hard here's their resistances and weaknesses:

Primarina is 2X weak against poison, grass, and electric, they resist fighting, bug, fire, water, ice, and dark and are immune to dragon.

Incineroar is 2X weak to fighting, ground, rock, and water, they resist ghost, steel, fire, grass, ice, and dark and are immune to psychic.

Decidueye gains a ghost typing later so they will end up being 2X weak to flying, ghost, fire, ice, and dark, they're resistant to ground, water, grass, electric and are immune to normal and fighting.

I normally choose the starter that can sweep through the bosses with as little difficulty as possible so that usually means either fire or water for me. Although really it depends on your fighting style, I prefer going all out and just obliterate my opponent as fast as possible which appears to be Primarina's thing since the moves she learns can at the very least knock out the elite four easily.