I know there have been several more recent threads about storage, but I wanted to use this one to add my recent experiences with hygrometers.
So hands down, an electronic hygrometer will be more accurate. If you have a lot of puer stored, by all means go digital. Since I have a few smaller sealed containers of puer, controlled with humidity packs, I willingly accepted the risks of analog hygrometers, because I wanted a small, unobtrusive hygrometer for each case. And I've heard some Chinese storage obsessives fret about electromagnetic radiation near puer, so this ought to make them happy too.
The hygrometers first need to be calibrated: if you place them in a freezer bag with damp salt for several hours, the humidity ought to read 75%. See here.
Apparently analog hygrometers can also get "locked up" and need exposure to a high-humidity environment, like near your tea kettle. I can imagine many negative commenters on Amazon are not aware of these two facts.This one
consistently read about 5-7% low for me. The back unscrews for calibration, though you need a Phillips size 0. This one
was only a couple ticks under 75 when I calibrated it, but then it seemed like its response range was condensed--it read too high when it was dry, and not high enough when it was humid. You can calibrate it with needle nose pliers.
I just got an inexpensive electronic hygrometer/thermometer, and that should give me more confidence about the accuracy of the analog ones.