The subject of calibration and comparison can be very confusing. I prefer to leave things alone and if I need to adjust, do so in accordance with the owners manual. The comparison of 2 stations can be very tricky. I'm currently running 3 (Rainwise, Davis Vue, Lacrosse 2810) and each data point can vary from time to time. For me as long as each are within a 'reasonable' range, that works for me. Not only do you have to consider manufacturer, but you also need to factor in mounting location.
One item I've noted in physical observation (not to be consfused with reading the display), the Rainwise station, by far, is more sensitive to wind/air movement. Not to say that the Davis Vue doesn't pick up the winds it should, but I've seen cases where the Rainwise props are spinning like crazy and the Davis (only 20-25' away) is hardly moving. I attribute most of this to wind funneling in my backyard. I think I understand and can accept this. But the Rainwise wins the overall sensitively award. Even my hand held weather sensor agrees. Heck...even the Lacrosse 2810 cups can read winds under 1 mph.