As many of you know,I tend to give all my business to AC.I needed to be in Chicago for a meeting this Friday past.Mrs.acysb87 and my daughter decided to join me for Fathers Day weekend in the windy city.
I left the bookings to my TA and ended up on a UA (AC codeshare flight) today from ORD to YYZ.( I had asked for assistance to try and get E Plus seats ,alas there were only centre seats)Here is my unscientific comparison of the 2 carriers on this short run.I was in Y on both segments

UA ^
Priority security line for *Golds at ORD(not so in YYZ for * Golds)
Bag Snack Mix AND Granola Bar on flight are complimentary(on AC you pay)
In flight audio listening to ATC(not available on AC)

AC ^
After not having E Plus available ( middle row only),in-charge allows passengers to re-locate for better seats with more room. before departure.
AC got me the emergency rows
The aircraft interior was in a retro color scheme that reminded me of Austin Powers (or parnel )(the mainly AC green suits me better)
AC blankets were clean,the UA blankets smelled poorly (daughter sent back unused)Generally,the AC aircraft was better maintained ,IMO.(piece of UA floor piece measuring 16"x4" x1/2 thick came loose at my seat)
Heatsets new on AC,reused on UA (my daughter is going to Western to be an audiologist,and gave me an idea of all the diseases possible with reused headsets )
AC has CUSTOMS FORMS ^ ^ UA is backordered 8 weeks .(I guess they think they are not coming out of bankruptcy protection )
Everyone entered customs hall and not enough tables for everyone to fill the forms out.

Both airlines get Priority bags out after everyone elses bags