If you’re starting soon, I think I would try and bid the A220 since about half of the 220FO seniority list through the end of 2022 will be pilots not here yet. I think I read about 6 just started today and got assigned the A220, so they’re in a pretty good spot IMO.
A220/A320 upgrade time is about 6 years now….not sure where 9 came from. I think when the Covid dust settles it’ll be around 4-5 years, maybe a hair shorter on the A220.