I am not a CFA. The following is my personal opinion: I like BNS and BMO most.
Here are my reasons:
1. BNS is the best among the five bigs for it ROE (~20%) and Effection Ratio (< ~55%)
2. BNS is most diversed "international" bank
3. I like its business model: focus on emerging countries - higher ROI. It comes with higher risk, but is offset by its diversion.
4. BMO has been building moment for a couple of qtr. Its P&C division gets record earning every qtr with best growth rate (~20% y over y). It is not surprise if you see earning surprise this coming qtr (Aug 24th)
5. You will be well rewarded if you do BMO DRIP (2% discount - I believe)
Good Luck