Then I would add that one of the criteria would be, how necessary it is for you to get that position. If it is a once in a lifetime chance to get a great job, then consider everything together. If it isn't, I would be very careful and do even more research before making the decision to move. Include pensions in this too as you may end up with a bigger gap.

If you have a permanent job now, and you like it, then it is an enormous amount of upheaval for your family. These are always difficult decisions and the problem if you move is, you won't know for ages whether it is the right choice. If you stay, you have to ask yourself, have I/we missed a great chance?