I'm not sure it's true that one is better than another. Remember that you can budget any category of scouting to a maximum of 20 million. Maximum doesn't mean perfect or accurate, just maximum. There's fuzziness at 20 million.
In my experience, 10 million scouting is a waste of money. Any projections you get from that are guesswork. 10 million better be a stop on the way to something higher or lower.
Advance scouting is probably a little more projectable than College scouting than High School scouting, just because of the ages of the players involved. The time factor. Projections are targeted to age 27 which is when most players stop developing. So if you're looking at a 25 yo with 20 mil advance, you should be pretty close. An age 22 college senior is five years out. An age 18 high schooler is nine years out.