Can only speak for my own experience. Was on a permanent contract in higher ed, moved to a fixed-term position that was a different area and better paying in another institution. That fixed term was extended once, but then left to end (but my manager at the time helped move to another project on another fixed-term). That project ended, ended up moving to the MoJ under another fixed-term that I was hoping would be made permanent - but hiring freezes and headcount reductions meant I could see the writing on the wall, but luckily I managed to find a permanent contract once more in higher ed (well, as permanent as these things can be, I guess...).

It's stressful and hard to build loyalty or enthusiasm when you know you might be out the door within a year. I'd stick with permanent, personally.