I think the edge is doing which side you favor. If i was looking for the reds to go over. I'd bet on 4. and if the odds were 4 1/2 and 5. I'd bet on the site that offered 4. And find the best line for price.
it depends and as other said its best to go with the best odd/line you can get.
When I began betting I used to be deceived by the lines, say I wanted to bet over x and found that the lines was too high, say 2.25 I usually didnt bet or just took the under, or even went to other book, went for middles etc.
The thing is the books dont have it that much right most of the time and they just set up lines and bets move them, and has nothing to do with the actual game, bet should be determined by your stats/analysis rather than line compared to other books