The figures quoted by CEJM are correct. As a junior bod at BA you'll most likely do blindlines to begin with which means invariably you'll be flying every (or virtually) every weekend. The upside is that you tend to work slightly less than CAP (the target number of credit hours that BA set for us each month, usually in the mid to high 80's). From my own experience on the 777, on a blindline you can't really bank on picking up an extra trip each month. The reason being is that the overtime trips available nearly always fall over the weekend which seeing as you'll be working then anyway means that you can't obviously do it. I'm not sure if it's more feasible on shorthaul, over to someone else for that one! Also, on a blindline as you'll be a bit under CAP you only get the full overtime rate for the amount your new trip takes you over CAP for the month, so it may well not be worth doing essentially. As with everything at BA, the rules are complicated and will take some time to get used to, expect to make several errors before you get the hang of it!
For someone coming from easy to BA, I would suggest that money shouldn't be the motivator. Assuming you have, or expect to shortly have, a command at easy, the money £92.5k ish vastly outshines the initial BA salary £61k ish inc allowances. Sure, the BA salary goes up £2.5k ish each year but you'll be many years off command, maybe 15+ for a longhaul command anyway, not sure about shorthaul, less obviously. The BA Capt Salary is higher than that at easy but you'll be waiting a long time to get there which makes it more of a close call over the course of a career. BA pays in 12% of basic into your pension pot which I believe is a bit higher than at easy of 7% I think?
All in all, it's an individuals choice, lots of good and possibly not so good things about working for either company. I have several friends from my flying college days who are at easy, happy and have no intention of moving anywhere. Personally I'm reasonably happy with my lot at BA (it's testing at times for sure) though from chatting with my mates at easy I can fully appreciate why it works for them. Anyway... hope this makes the financial side of things slightly clearer.