I used both; the feel and the gauge. What i do, i record every pressure (+- 5psi within 30psi) and drive for a few weeks on each set-up and feel which is the best for me and i will used that reading every time i check my tyre pressure. So, for me the gauge is necessary and i used the same gauge every time, every where.
By the way, i'm using the analog PCL gauge only. bought from the van that supply tools to workshops. They normally go to every workshop to market their tools. Coincidently i was there and i bought it for RM12. The last one i bought from hardware shop in ipoh for my sister cost me RM25