I did it, left a relatively senior FO position at BA to work for a low cost carrier in another part of the world. There is no easy answer to your question, I left for family reasons and have never regretted doing this to spend more time at home (less night stops) etc. I do however really miss BA, you are looked after very very well there, if I had been able to stay at BA whilst making the family situation work out I would have done that. I got a very rapid command in my new airline and now check and train as well, in my opinion I wouldn’t swap airlines if your only motivating factor is time to command, being in the Left hand seat is good but in no way outweighs what you would be giving up. BA training, bidding and contract are still of a very high standard and your months and years of seniority are hard earned and can never be gained back. Think of the overall picture as well, my mates at Easy find little things annoying like no staff travel outside of Easyjet, inability to experience Longhaul etc.