First, you'll want to ignore anything that JS says. He is delusional and a blowhard.
Second, I am more of a speed guy as demonstrated by my PRs: 4:00 15 but only 15:30 5k. That being said, my best marathons came when I basically trained for a 5k, but added a weekly super long run up to 22 miles. I never did any marathon pace stuff, just T pace and I pace stuff. (Using Daniels tables) Like 10x800 or 5x1600 at 5k pace and 4-5 mile tempo runs. The super long run was the most beneficial for me. I had the speed, but had to really work on the endurance.
I also had to really work hard to negative split the marathon. It was painful to have to slow down to what felt like a jog for the first half, but it paid off in the second half a when I could keep pushing hard all the way through. I think speed guys get sucked in to a too fast start because of how easy the first 10 miles can feel to us. I had to learn this lesson the hard way.