I have been a machinest/tool-diemaker for over 20 years, on the calipers, I have used several brands over the years, the Mitutoyo digimatic are the BEST hands down, they do not get dirt in them like a rack and pinion caliper, they are extremely accurate, and they do not get the mechanical wear down in the small size range that mess's with mechanical calipers.
a 4" set of mitutoyo should do almost all reloading tasks...and the battery lasts me 6 months to a year and I never turn them off.
The ID measurment on the Mit's is amazing, I have had access to ID Gage set rings and every set I ever had was within .0005"
I would not scrimp on a powder scale, or on measuring tools, also needed is a 0-1 micrometer with .0001" measurement.
Bill