From Calgary, I would say outbound, certainly EWR would be the best. Train to downtown is fast enough, and the timing is good- leave YYC around lunch time, arrive late afternoon.
Return, I would say LGA. The departure time of AC's EWR-YYC is quite early, so if you want to work half a day (or just not wake up by 5), LGA is better. AC has a good operation at LGA, with lots of flights, staff, a lounge, priority security, the works. There are many flights available all day via. YYZ and YUL that would make connecting painless. Also, after a long business trip, being able to hop into a cab for a short ride to LGA sure beats a long train ride/taxi ride, to EWR.