Originally posted by Phoenix 17
Cloud has both had Jenova in him, and travelled the lifestream, yet amazingly he doesn't even hint at being able to read tea leaves. Sephiroth, although admittedly more exposed developes global ESP, the ability to control super powerful ancient aliens a tiny fraction of which is the reason for his strength, and apparently the ability to mutate and grow wings.
But wasn't it explained in the game that Cloud became who he is because of his weak state of mind? Something along the lines of those who are infused with the cells of Jenova become stronger. And people in a weak state get lost in the process. This could explain why Cloud did not gain any special abilities or knowledge (besides regaining his sanity) when he fell into the Lifestream.

However, I can definitely see both sides of the argument. Sephiroth could have become enourmously strong while floating in the Lifestream, or Sephiroth could have gone through the same experience that Cloud went through. And since he had Jenova, she would have most likely poisoned his mind beyond repair. There doesn't seem to be very much, if any, proof to back up either claim. But it still is interesting to talk about it.