This is the best win condition in here. Although it can be countered, It also can serve as mass removal if your opponent's board state gets to be too much to deal with before you combo out, given that you ramp properly, aside from the fact that it explodes with infinite mana from any of the untap loops.
With any untap loop, Fireball deals infinite direct damage, which can be used to nuke the field in the case of agressive board states similarly to Comet Storm. It is not as good as removal IMO because you do more damage to more creatures for the same amount of mana with Comet Storm, but it still goes boom with infinite mana.
Braingeyser can be used to fish for a win condition or combo part in addition to milling out your opponent with infinite mana