You cannot simply look at openers and closers either, that is the problem. You have to look at the BEST number, be it opener, closer, or somewhere in the middle.
This year has been a small anomoly in terms of expectation. It is almost a 3% difference for a one point "better" number overall. Generally it is a little over 2%. (assuming the BEST number available) which isn't possible to get every time.
Vig is more important than spread, that is a general rule of thumb to carry with you.
When people can't even agree on what the best number is/was, then trying to figure out the specifics is impossible.
Half the guys will tell you they got -4, while some guys with exchanges or a rogue books got -3.5 at some point. (both assuming -110). While some will say they took -4 -110, but now can get -4.5 +103. The people will try and tell you which is "better". When there really is no answer. Although they will continue to cite how much Pinny or other books charge for a half point or a point, which is irrelevant.
There is no secret formula, the less you have taken out on a win is always the best policy. Or the less you risk up front for a better pay off on a win (depending on if you lay 110 to win 100 or 100 to win 90.90).
Unless you aremaking thousands of bets or thousands of dollars, then even that (vig) is slightly overrated.
So best explanation is spot better should get best spread with best vig, and long term players should focus on best vig first, then best number.