The three main starters are Bulbasaur, Charmander, and Squirtle. However, if you walk away from those three four times (since they are immediately available once you start) a Pikachu will appear. In the end, most people agree that the starters aren't a huge deal since you'll get better Pokémon very quickly and even better versions of all four as they can be readily found in the wild. The three teams are Mystic (Blue/Articuno), Instinct (Yellow/Zapdos), and Valor (Red/Moltres). Right now, I think the most popular is Mystic. Thus, Mystic is also the most powerful. However, Valor used to be the most powerful. Instinct has always been in last, but is slowly getting a lot of support so we'll see where things go. Base you starter on your preference and your team on your friends. Most Bungie.net people I know are on Valor (though Mystic would make more sense since Bungie likes blue, but whatever).