I live in Mississauga which has used articulated buses for decades and they are troubled by high maintenance costs.
And in terms of operation, the lower frequency means more people waiting at stops, loadings times are longer, so bus are slower or fall behind schedule easier, which lowers the frequency and capacity of the route or increases the operating cost to maintain the same frequency and capacity. Buses may be longer, but still just one door for boarding.
Articulated buses also cannot operate when it's snowing heavily. They get stuck in the snow very easily
as Ottawa learned the hard way. I have personally been forced off articulated buses because they got stuck in the snow. But Mississauga Transit just keeps them in the garage now when it's snowing.
So based on my experience, I think articulated buses should never be used except for limited stop routes, especially with all-door boarding scheme. But this is still Canada, this is Toronto, it still snows, so you can't have a fleet with too many articulated buses or there could be shortage of buses when there is snow on the roads.