While I wouldn't place too much stock in the info given in any individual bettors guide, those who publish them do so after careful consideration of things like pedigree, a horse's current condition and track conditions. Consulting with bettors guides probably brings a better chance of doing well at the Kentucky Derby than simply betting on the odds alone.
If a person is a beginner at betting on the horses, then the best bet is to make a safe bet in line with the recommended choices which can be found in a bettors guide. The betting authorities are well regulated and tend to provide the most accurate and comprehensive guides to each horse.
I do feel that a bettors guide can indeed help you to pick a winner in the Kentucky Derby. By having the extra knowledge and information at your fingertips you will be better informed to make a choice based on statistics rather than just on a hunch or a guess.
A bettors guide may help you if you have no clue about horse racing and it will give some tips and information that could be helpful but if it actually was shown to statistically increase your chances of winning, just think about how much money those things would be worth.