airoli

Hello,
hope you can give me advice. I need to fly to Chicago in early October and there's no more youth fare direct flights out of Zurich. But they offered to fly me via Brussels for the same price. Now I have the choice between a AA or SN flight BRU-ORD. Which one should I take, and is it worth to burn 25000 miles for a business upgrade? Also, when I take the upgrade, can I use it on all flight segments?

Thanks,
Oli