IMO if a game opens at -2 and moves to -3, the money line lags behind most of the time. The moneyline may even be equivalent to -2.5 in same cases and it has happened. I've found that the book I use (Bodog) likes to have the favorite .5 more but this isn't reflected in the ML. Spreads move because of money. ML's move because of money. Sometimes more money comes in on a spread than on a moneyline and visa versa. In the long run it would be beneficial to know whether to take the ML or the spread because value can be found in one or the other. If the books are doing their job right, if you were to play every spread opener and every ML opener for those same games IN THE LONG TERM you should be at about the same + or - although there are bigger swings betting the ML.