Sonny said:
The differences in win/loss/push percentages were only slightly different at one decimal place.
This is true; the differences are always small because at the point where a decision might switch, the two options are always very close in value. Furthermore, as you take into account the probabilities of hands appearing, the differences in EV get evened out in certain cases - the probability of busting if you hit 12 vs. 3 goes up with the TC, but the probability of being dealt that hand (P(10)*P(2)*P(3)) goes down.
As a side note, this is why insurance is ALWAYS the most valuable index change - the probability of an insurance decision is much higher because it's a one-card probability (P(A)) where as all the other strategy changes are three-card probabilities (e.g. P(10)*P(6)*P(A)).
Ultimately, what makes indices valuable is your bet spread. Standing on hard 16 vs. 10 might only net you 0.01% difference, but if you have a 10-unit bet out and are playing at a 1% advantage, that's an increase of 10% to your win rate. This is also why the I-18 is only a rough rule: depending on what you bet at each count, the value of a strategy change will really change.