I would probably use a PT100/PT1000 sensor, they are easier to deal with than thermocouples and much easier to calibrate if you're going to design the signal conditioning and do the calibration yourself. Make sure you select one than is rated up to 1000°C (they will not come cheap). They are often also easier to integrate mechanically as you can find them threaded. Now I'm not sure you can reasonably get better than 1°C of accuracy over a 0-1000°C range with them, so that would have to be checked, but a possible show-stopper.
Thermocouples sensors alone will be cheaper but much less easy to integrate unless you buy ready-made and pre-calibrated modules with signal conditioning...
It will eventually depend on all your requirements, so take a look at both solutions and figure that out.