mmm I would give my vote to Lance because Although he uses dragonair twice, which i think its a waste, he has quite a good combination and a variety of pokemon, like gyarados (water) and charizard (fire) as well as aerodactyl, which is a terribly strong pokemon (as long as you do not have a water or electric pokemon XP).
Also he's quite cool, like in pokemon gold where he works with you against team rocket ^_^