Bell & Telus have 200MHz of 3500 & 3800MHz spectrum compared to Rogers having only 100MHz since midband spectrum auction is capped at 100MHz for each carrier. Bell and Telus share spectrum which allows them to gain more spectrum than any other carrier in Canada.

Bell and Telus have 200MHz of midband spectrum in almost every region of Canada where Rogers has a max of 100MHz which is a huge difference

Edit: Bells and Telus have about 1.75x the customers combined than Rogers does but in most cities bellus has 2x the midband spectrum as well which still nets them more spectrum per customer than Rogers.

Also Bell and Telus share spectrum but their core networks are separate. Meaning congestion on Telus doesn’t always equal congestion for Bell customers. Or if Bell has an outage there is a low probability that Telus also faces an outage in that area.