Does your company have any corporate travel policies that would influence who you fly?
What are you goals from having status? Perks and/or redemptions?
Do you book your own travel?
Paid by you or via corporate card/travel agent?
Where will you travel to most?
Same for hotels?

Any credit cards?

ORD is generally owned by either UA or AA. Depending on where you’re going most, the schedule of each airline to those most common destinations and personal tastes different airlines work better for different people. AA, in general, treats elites better but if AA has limited service to your primary destinations that doesn’t mean much.

If nothing else, it’d be wise to do an AA challenge off of your UA status so you have something. Be sure to check if your company has any existing arrangements with airlines, hotels & car rental companies.