I know plenty of people who have left their command to join BA. The calculation involved is, of course, a very personal one. Increasingly though Captains at easyJet and Ryanair are in their mid to late 20's/early 30's. That still gives you a 30+ year career at BA and even a pessimist would acknowledge that some of that is likely to be as a long haul P1.
I acknowledge it is a more balanced decision with the birth of 34 pay points and the expansion of the seniority list. However it's a long term decision and for most people will be about lifestyle as much as money.
Best of luck to those waiting for the call!