With an outlook of 2-3 years at either company and your age - stay and work hard on the upgrade and fly those hours as CP asap.
If you are looking to better your "market value" and thus higher pay in the long term you need command time.
As stated below, only in hindsight will you know, what decision was/would have been the "right" one.
Good Luck!
Last edited by wonderbusdriver; 13th Dec 2017 at 17:03.