honestly, with a cum laude, i wouldn't be too hopeful of your chances of securing a back office role at BB. the competition nowadays for a BB back office role is more intense than most of us imagine it to be.

and the truth is, BBs dont preach and practise internal mobility. once you're in the back office, you're most likely than not stuck there forever. there's practically no chance of you applying for a transfer to MO or FO.

i would say, take the big 4 consulting role if you can (despite the lower pay) and work on things from there. it might not bring you that much monetary satisfaction but i think in the mid to long term, it will open more doors for you.