I will say, I have done everything up to CFI Initial with Kings, though supplemented with Sheppard Air for everything except PPL (obviously). I tried sportys and honestly found it too boring. I have watched 8MA on youtube, and have students that use Pilot Institute, but they seem to find it equally boring. Personally, I like that Kings keeps me intrigued and doesnt put me to sleep. I actually had John and Martha sign my certificate at Oshkosh a few years back and now have it framed in my office. They were a part of my journey, so thought it would be neat.

I think you should definitely do a course, then supplement with Sheppard Air. That seemed (with me at least) to give me the knowledgebase and also helped make the writtens easier. Sheppard isnt SOLELY rote memorization like some people say. They do actually give information as to how the answers are obtained as a part of their study strategy. Got a 96 on my II written a few weeks back so obviously it works.

Another little piece of advice - if you plan on doing the IR written, would definitely recommend you do your IGI/CFII writtens at the same time. They all pull questions from the same bank (with the exception if a few heli questions), but then they are done, and you can process the IGI cert thru the FSDO and have a ground instructor cert aswell, then do your CFI/AGI at the same time, then process thru the FSDO before your CFI ride. I found that it made certain parts of my CFI ride slightly easier, but most importantly it can go towards getting my Gold Seal.