It is not even a close decision, do the SH command at BA and then come as a direct entry captain. Jet2 Captain in your local base is among the better jobs in the UK at the moment (albeit still significantly underpaid compared to competitors), the same cannot be said of life as an FO/SFO. Yes, you might get a command within 18 months, but you probably will not, it is not a reliable system and the 80% command pass rate quoted above is a company figure that does not hold up to any scrutiny. Reference: I work here.