Well, you can make chess engines give you a numeric evaluation for several possible moves. These are typically tuned so that the value of a pawn is around 1 point. A grandmaster 1 or 2 points ahead can routinely convert to a won game, assuming he doesn't blunder.

So if the best move has an evaluation of +0.05 and the second best has -0.02 , the difference is probably a very subtle positional improvement (and the first move may not in fact be better; chess programs aren't perfect). If the best is +3.12 and the second is -0.02, and you can't see why, there's a concrete material tactic you're missing (or, less likely, a major, obvious positional devastation).

But, it can't tell you what you're missing, just the magnitude of the difference.

Compare all you want ... that doesn't tell you why the choice was made, because it was made by evaluating and comparing many millions of positions.