I choose water because of it's wide variety of move types, depending on the starter. Say, with Squirtle and evolutions, I could learn Ice type moves like Blizzard and Ice Beam, via. TM's. Ice is super effective against Grass, and Water by default OWNS Fire.
Don't let bias ruin your vote. I prefer Grass types, but made myself face the truth.
I declare myself the official Irvine of the Final Fantasy XV board!
Fire seems to be the way to go. Water pokemon are a dime a dozen, and grass pokemon are way more common than fire. So to have greater type coverage earlier, it seems to me fire is the way to go everything else being equal.