Without a second thought, I'd pick Cloud's side.
Sephiroth doesn't seem like much of a team player. I think he'd just as soon strike you down if you got in the way. Not to mention his complete obsession with Jenova, which would get old really fast.
"I'll reclaim the planet for Mother. It was hers first and they stole it. I'll get it back for her. Mother wants you to help me."
".....Mother also wants you to put on this slave costume and dance for me."
Boys overly controlled by their mommies don't interest me much anyway.
