It is best to use 0.1N NaOH since you can overshoot the required pH while using 1N NaOH.

Thank you Nitin Fadnavis

Either can be used :) But with 1M, you risk that the pH will jump too high or you risk that you will need to much of 0.1M NaOH. It depends on whether your solution is buffered (and how much), what is the volume of your solution and how small volume are you able to add.