I'm assuming the 1 micron scales would give me 0.005mm increments on the cross slide display rather than 0.01mm increments from the 5 micron scales. Worth having or not? Agreed about it being resolution rather than accuracy but in theory I could maybe half the uncertainty.
1 micron scales should give you 0.001mm increments but it's not worth spending more on them because 1 micron resolution does not mean 1 micron accuracy. Check the spec of the scales for accuracy over 300mm or whatever you'll find it's way more.
Resolution is just what numbers it will put on the display. Accuracy is how closely it reports those numbers compared to true distance. Most manufacturers state better resolution than the scales are capable of reporting accurately because - why not? As I said above, it's academic if it's going on a lathe, even a Hardinge. For a grinder, you might be justified.