If you get stuck on the bus you will get 8-11 days off. Combination of medium and short haul and flipping from front side to back side flying. For your 8 days of you will fly 80-85 hours per month. Once you get MFF qual'd, life improves a bit but not much. You will use your 8-11 days off to recover from flying.
Just 330 flying will send you mainly to Africa and India. Rarely to Europe and that's it. It is hard, you will be tired. 80% of layovers, when you get them, end with a red eye back to DXB. Night India turn arounds will kick your a$$.
340 flying will also send you to Africa and to China. No more ULR. The longest flight you do will be Dakar or Shanghai. Both about 10 hours depending on winds. You will be a little less tired but not much.
Good luck with your decision.