I chose Amoonguss for various reasons:
Amoonguss looks like some Pokeballs, and I love Pokeballs.
Alomomola is a water type, and my main Pokemon is always a fire type, so I hate water types.
Amoonguss was shown in Pokemon BW: Rival Destinies, and I don't think Alomomola was (though I might not remember it, or seen the episode it's in yet ) and I love that show. Along with the others, of course. :D
So Amoonguss rocks for me.