I have done king for all my written test...PPL , IFR, COMM, FOI, and I am going to be taking the AGI and AFI in the next few weeks. What I do is review all the king videos, then when it comes time to go through all the material at the end, I get sheppard. Only one I didn't do sheppard for was PPL (98%), but that was over 14 years ago, and they had just stopped publishing the answer banks. The rest of the written test I have taken have been in the past few months. I do exactly like they say to do, and the lowest score I have made so far is a 96. Took the FOI last week and made a 100 on it. That one is pure memorization, and I just kept pounding those questions over and over again till I didn't even have to read them all the way through to know the answers. The kings teach you the material and sheppard helps you memorize the answers to the CURRENT test bed. Literally every time you fire up the software it will check for updates. If you study the material for a week or two, it usually has atleast one, maybe two updates...That is how up to date it is. But it doesn't teach you the material. Even if you have a question and click on the "explanation" tab, it just shows you an excerpt from the FAR/AIM. I would regularly go back to the king and find that section if it was a questions i didn't understand how they got the answer.
I got the check ride prep for the PPL, IFR and CFI. I skipped the Commercial for that. The IFR helped listening to her go through her flight planning, and why she chose what she did. Fuel, weight, MEA, weather, alternates, etc. I could have done it without it, but for $120, i think it was worth it. I haven't taken the COMM or CFI practicals yet, but that practical test prep for the CFI has allot of info in it.
I have done almost all of my own ground school and if I had to pick only one source it would be king. You have the thing for life with free updates, so you can go back and refresh yourself in the future, which may be nice if you aren't an active commercial pilot. There is a reason they have sold over 2 million courses.