both are good
keep in mind actuarial co-op is the hardest co-op to get into since they have such a large candidature and only around 10 positions each year.
last year i made it to interview which already knocked out 80% of people, and there was still around 60-80 people left for the interview.
you dont wanna put all ur effort into actuary, just to not get co-op.
on your co-op application i would focus equally on commerce and actuarial / not make it too niche, so that you hopefully can get an interview for both degrees.