Nour, my understanding is that though foils may have a better tempco, precision wirewound will have better long term drift. Tempco can be compensated for, but the only solution for long term drift is calibration -- pick your poison. My plan is to (eventually) try both and compare
I actually don't know much about what you have mentioned to confirm it or not and also as you said I will try both.
But if wirewound is good enough, how much enough should be enough?, for example, is it good enough for LM399 or LTZ1000. if so I would go for it!
Originally I want two sets, one as a lab standard(1,10K) and the other set for building voltage reference standard!