An excellent letter in the Newham Recorder by John Saunders of Newham Voting for Change:

Under the committee system, the council leader would have to reflect the views of the whole council and be governed by the decisions of the committees – and every councillor would be a member of a committee.

This means that residents would have two or three local ward councillors who have real influence in the council and would therefore be able to represent their views and interests more effectively.

Directly elected mayors do not give their residents a greater voice, the committee system does.

https://www.newhamrecorder.co.uk/news/thanks-mayoral-referendum-cancer-champions-and-maths-fun-7911256