Round or Retangular: Well it is easier to DRILL a round hole, or CUT a Retangular, but it's easier to DRILL than CUT.. I'm serious that's the only differnece.
However I'd not recommend either of those meters, I would want at least a 3 1/2 digit meter (those are 2 1/2 digits)
1Y.ZZ like the plug in model someone posted a link to
(You ask what is a "half digit" well the 1, Since it can only be a 1, they only put in the segments needed for a 1, So that's called a "half Digit".
NOTE: Some meters are designed for use on 25 volt vehicles so they would be full 4 Digit meters (work on 6, 12 or 24 volt)
But the bottom is I want at least 2 digits to the right of the decmil. Since SOC is a matter of HUNDREDTHS not tenths of a volt .
