Noone mentions Aeroplan/AC Altitude because its the pits of frequent flyer programs (while its still a decent canadian credit card rewards program)

It really depends on the fare your work will be buying for you.
If they are cheap (tango) fares - careful - most wont earn much on Turkish, and status wont come fast when youre earning 25% or 50%. Only United still gives 100% status miles on all fares between Canada and the USA.
If they are expensive, last minute, business or latitude fares - you are best off with United for the insane mileage earning on expensive tickets, (or Aeroplan if you want/depend on domestic upgrades)

Redeeming with TK for award flights is also not a pleasant experience, and fees are high.