I'm currently doing maths/stats with actuarial studies. Although its a 4 year degree (comm/sci), I reckon its a pretty good combo as you learn more abstractly and gain technical skills out of it (from computing electives). Since its a degree double, you will be given an opportunity to get PART II exemptions as opposed to someone who is doing a straight commerce degree (unless they are co-op).
I'm not sure if its true but I heard that the second year/ third year higher maths subjects' scaling make it easy to attain HD's (if not then D's) so it can be sort of a WAM booster.
Finance: do this as a major if you want the easy way out.
Accounting: this major is a lot more theory based than finance/ actl. A lot of people find first year accounting courses dull. But as mentioned above, it may improve your employability (back-up).