Three choices:
Doug Ford. The "risky choice." Very much a loose cannon. Would be an outsider. Had a lot of support in the suburbs of Toronto (especially Etobicoke and Scarborough) when he ran for Mayor, but municipal politics is non-partisan and that throws a potential wrench into that equation. Can he win in the 905? Can he win in rural Ontario? How far can his very suburban Toronto-based populism take him? Don't know - which makes him risky for the PCs.
Christine Elliott. The "safe choice." Lots of experience, probably significant support in the caucus and in the wider party, probably making her the easiest to just slide into the driver's seat. Mind you, she has the millstone of having already lost the party leadership twice around her neck, and also the optics of having left politics to accept a patronage appointment from Kathleen Wynne, which will probably be thrown at her by Ford.
Caroline Mulroney: The "intriguing choice." Successful career as a businesswoman. Lots of name recognition. That can work both ways. Brian wasn't very popular when he left office, but personally I think he looks better as time goes by. She has lots of potential, I'd say - but little or no direct experience in politics. Already had a nomination under Patrick Brown's leadership, so she's not exactly like her dad who basically would only run if he was the leader.
I've been reflecting on how this might affect my vote. As I said above because I am very impressed with Laurie Scott - my PC MPP - I've been planning to vote PC. Since Scott is my reason, there's no one the Liberals or NDP could nominate that would change my vote based on the local candidate. Unless one of them takes some really unexpected policy position, I can't see that either Elliott or Mulroney lose change my vote. But I'm not sure I could stomach voting for a PC Party led by Ford, no matter how much I think Laurie Scott deserves to be re-elected. That outcome would likely lead me to the Greens, since I think it really is time for the Liberals to go, and the NDP under Horwath have never really impressed me - although with Ford as PC Leader I'd be open to being unexpectedly impressed by Horwath. Wynne would have to go a long way to impress me enough to get me to vote Liberal.