It's been a long time since I used a pH meter (30+ years).  The electrodes
should be pretty much of a standard nature.  The electronics, to which the
electrode is connected will make the difference.  Virtually, everything
today would be digital.  The question becomes how many digits of resolution.
You also want a unit that is temperature-compensated.  It should be of a
low-drift nature.

Accuracy, will depend on how you standardize it.  If you will be testing
solutions of a known low range of pH, then a standard close to the target
value should be used.  If testing at a wider range, a second standard can be
used, and a (control on meter) adjusted to zero in on the 2nd value, after
which a retest of the first value should be made.

HankG