At -110 a bettor must win 52.38% of the time to break even; at -105 the breakeven falls to 51.22%. That ~1.2-point discount is worth more than almost any handicapping insight, which is why volume bettors gravitate to reduced-juice books and promos. Watch the number, not just the juice: -105 on a worse point spread can still be the worse bet.
Reduced-juice pricing surfaces automatically in cross-book comparison: for the same market and number, the reduced-juice book's price simply wins the best-line comparison. Computing per-book vig from the feed identifies which books are running cheap on which markets right now.