500ohm VR will make it a little less "jumpy" when adjusting over ~1.35V.

When you're using 1K VR you have to be more carefull turning the pot cause a little dial means more voltage than with a 500ohm over ~1.35V.

I did set my 1K VR to 500ohm before soldering so a 500ohm VR is even better than 1K actually.