In pro football the computer power ratings are not that important. They are much more important for college football because sometimes teams don't have common opponents. I don't think power ratings are that important. In some sports there are things that are more important than the total amount of individual talent on the teams. By and large, however, when one is handicapping sports, talent is the overriding factor in determining the point spread.
Talent is the most important ingredient.
You said that statistics play a surprisingly small role in odds-making. The idea sometimes has been quoted that the odds-maker's goal is to split the money with the line, so that equal amounts are wagered on both sides of a bet because then bookmakers will use losing bets to pay the winners while keeping the vigorish as profit. The odds don't necessarily agree with how we think the teams will perform. By and large, however, the two approaches become the same. The odds that split the betting action on the game actually coincide with how the teams perform.