There are other considerations:-
1. Which is the better employer?
Terms and conditions are very important and need to be considered.
2. Have you flown long haul before?
Without the experience you will not know how you own body reacts to jet lag vs the early/late routine of short haul.
3. Do you have a low boredom threshold?
Sitting up all night in a B747 can seem to some folk like having a frontal lobotomy.
4. Do you have a family?
They need to be consulted about lifestyle changes.
5. How hungry are you for a command?
The novelty does wear off for some people; you might then be stuck with a duff airline.
Finally. with 27 years to go you have plenty of time to go so you can try different things. However, if the B747 job is with a moajor then the opportunity may not come your way again.
Best of luck,
SOP