Unless you are very familiar with the cartridge and powder that you are using it is best to start with the starting loads. The load books are not a recipe book, but rather a guide. If you do use multiple manuals and have conflicting data either start with the lowest starting loads, or (and you should do this anyway) look at the details of their data. The bullet diameters, barrel lengths, primers used and so forth. Many times it will become clear in the details of the whats and whys. Then you can extrapolate your start charge.
"Always place your clothes and weapons where you can find them in the dark"
"Understand that the enemy is not the enemy in his own eyes ;this may offer you an opportunity to make him your friend. If not, you can kill him without hate, and quickly."