Welcome to AA. You're asking questions that will, in general, be hard to answer.

The first is easy- no match, so do a challenge (and don't blow it this time )

As for the upgrade questions- I'd suggest reading here as these have been asked many times, and there are many anecdotes on both sides, and nothing even close to definitive. Do note that ORD is a hub for AA, and it is reasonably EXP-heavy, so that will have an impact on upgrade %.

Others can answer the airline comparison.

Cheers.