Well, flip a coin. And what do you wanna know about Pokemon Stadium 1 and 2? I have both. In 1, you battle the kanto gym leaders and then elite four and then rival. Then, there are some cups you have to win using different level Pokemon. Then, you get the Doduo Gameboy which lets you play Blue, red, and yellow up to twice as fast as regular. The, you fight Mewtwo. The, you do this all over in round 2 and you get Dodrio so you can play 3 times as fast(which is REALLY fast!!)
2's basically the same, just more gym leaders and slightly different cups. No Mewtwo... And you can play r/b/y and g/s/c.
props to pokemonruler for the sweet sig and avatar