Congrats on your new building.
I would suggest that worrying about 5 vs 8 % fees is not relevant in Hamilton. If you can find someone that will keep your building full of paying tenants then it's worth a lot. You can't get this for 5 % on a small building.
You really get what you pay for and in your shoes I would plan on your cost being +10 %. (+ 8 percent, + GST, plus locator fee for new tenants is going to be at least 10% over the course of a year. ) And plan on changing most of the tenants in the first 2 years which is 6 locator fees !
But when you find a PM that you like, wow, enjoy it ! They earn every cent they make and I can't believe they make anything in the first year.
I had poor success with someone in Hamilton (not on your list of 3) and have recently moved to Cornerstone. I am very happy with their start.
good luck
Dave