I have 13 manuals total, counting bullet and powder manufacturers(a few shotgun books in there also). After eyeballing the Quickload program for about 2 years, I just bit the bullet and ordered it yesterday. So many bullet / powder / case / primer combinations that you end up just making a educated questimate using book data.

That being said.......
I reference Hodgdon's Online all the time. Also Alliant Powders site.
I like the variety of powders shown in Lee Precisions manual.
I like the way case specs / drawings are shown in the Hornady book.
Berger has an excellent description of col adjustments.
Barnes is a little lite on data, but most(if not all) of theirs is available online.
Nosler is nice and tells you what the most accurate load they tested was.
Usually I can find a pdf online for specific calibers out of the sierra data.
The gun guide style books seem to be a compilation of data from several of the above sources.

Some, or most of the bullet manufacturers use quickload to generate their data. They may not shoot the combination that is in there book.

I am always leery of forum posted data found online. Generally if the data does not reasonably resemble data from a powder / bullet manufacturer, I will not trust it.

I also figure that book COL is almost worthless. Whenever I start loading a new caliber / bullet, I measure for COL to lands. Usually start at .005-.010" off lands and go from their.