It depends on what you want to do with the rest of your career.
Technicalities:
Doing AppFin gives you the exclusive right to FIN310. What value that adds, I'm not sure, others will be able to shed some light.
Doing Accg (official major) gives you the exclusive right to do ACCG323 (shit unit, but got to be done), and be eligible for CA/CPA.
I honestly think Accounting is a very strong foundation, even for all things financial. As electives, you can do all the cores of the AppFin degree (whilst you major in Accounting).
So, instead of doing bullshit subjects just to make up credit points,do stuff like ECON200/201 (which is the gateway to 300 Level Finance), ECON141, then ECON335/350/360, ACCG329/352/353.
If you have THREE 300-Level units, that's a solid foundation in Finance, and then you will have your major in Accounting as well (by complying with all the requirements of that degree). This is what you should discuss with Bill Blair in the Accounting Department, he's a great adviser.
Otherwise, you can do AppFin and not worry about the Accounting. It may be more recognised in the finance field, and instead of doing Accounting cores, you can do a variety of finance and econ subjects for greater depth.
The decision comes down to what you want as a career. Hopefully AppFin students would be able to elaborate on why they chose their degree, as it is an equally valid alternative to Accounting.
I have an entry level position within the Asset Management business of an IB. In my division, they are mostly accountants with further studies in finance. So they did both. I've had interviews at the Investment Banking part of the business, and they seemed to give a lot of credence to Accounting. More so to Law of course.
All in all, it's what you see yourself doing 5-10 years down the track.
The way around the tough choice is to do one undergrad, the other post grad. Law is going to take long enough though