Short Answer: PatrickJMT. We felt like it served our kids needs significantly better than Khan Academy Math although we like Khan academy and used it semi-frequently.
Why should you listen to us on this subject? Of course, mileage will vary, but since using these programs, the kids described here graduated Magna Cum Laude in Statistics (Kelly) and Summa Cum Laude with Honors in Applied Mathematics (Christian) from a large state university. At the writing of this note (June 30, 2016), they are both midway through PhD programs at national research universities here in the United States. You can read more about that here.
Other posts about our math experience:
We found the instruction given in any one math program was not enough for our kids to fully “get” the concepts even though we used what we believe are the very best curricula: Singapore Math for grades 1-6, Teaching Textbooks for Pre-Algebra, Algebra 1, Algebra 2 and Geometry and Thinkwell for Pre-Calculus and Calculus. Someone asked us what we did in the higher levels of math when the kids got stuck. The question was asked particularly about the Thinkwell program, because they seem to provide less remedial, “make sure it is explained in more than one way” kind of instruction. The following question was asked four years ago, but I somehow (shamefully) missed it. You can read the the original question in context here. So, four years late, here is the part I missed and our answer.
Also, how did you handle any problems with the upper level Thinkwell classes your kids took? If they couldn’t figure a problem out, was there anywhere to go for help? My understanding is that, unlike TT, there is not an explanation for every problem.
Our kids, Kelly and Christian, have very different learning styles. Sometimes the things that were easy for Kelly were difficult for Christian and vice-versa. When they were in elementary school years that was not really a problem. We could handle arithmetic and the Singapore Math program was repetitive, yet interesting for the kids so they learned everything they needed from just following the program. As they moved into higher levels of math, they more frequently got stuck and needed some additional insight beyond what was available in the packaged programs. They got stuck in different places. At first, we pointed them to the Khan Academy videos. They were good, but some friends Christian met on the IRC Math Channel said he ought to try the videos at PatrickJMT. There was no comparison between PatrickJMT and Khan Academy. PatrickJMT was just better. I can not say that will be true for everyone, but it was certainly true for our kids.
Kelly and Christian continued to PatrickJMT after they entered their undergraduate degrees for help in more advance Calculus, Linear Algebra, Differential Equations, etc. We recommend it highly.