Have used both.
No. They aren't really necessary, IMO. I found the difference between the two to be less than the difference between rims.

The Trek 620 I purchased new, for example, had canti's and anodized rims. Braking was less than I'd hoped for until the anodized surface wore a bit, then it was better. Oddly enough, the 620 didn't have clearance for a fender on the front. It was a good bike, but not as good as it looked on paper. I weighed it "dry" but ready to go before the last tour I took with it, right at 100 lbs. I don't miss it which seems odd.

FWIW, on some long downhills in the Rockies (like divide passes), I found that by being up on the hoods with elbows out, I could keep it around 40-45 MPH, and at that age I was comfortable with that bike on those hills at those speeds.

I am older now, and might not find that to be the case. : - )


In any event, I think the limiting factor would be the rim's ability to dissipate heat - and a tire/tube's tolerance for it. Neither brake is going to affect that.