Not that it's much help but I was on the team that wrote the Avionics course for the RAF. We started teaching it in 1990 (Av Mech 1 where are you?) which seems like yesterday to me but is more than a pensionable engagement away. Aaargh.
I would say go avionics because it makes you sound like you're brainy. Riggers and Sooties always seemed to have hairy arms to me, you really don't want to be associated with them. I know people that associated with them and they developed scurvy.