There is no "Best" in brewing, just what works best for different people. There's going to be different designs but they're all going to be "BEST," for the people who use them.
The most "popular" one on here, and you can tell that by the sheer volume of posts is
this one....
But it works no "better" or "worse" than any other design.
get out of the idea of "best" in this hobby, there rarely is one way of doing everything. We have a saying in homebrewing, "ask 10 different brewers a questions, and you'll get 12 different answers, and they'll all be correct."
If you look on here for info, be it a recipe, or a diy plan or an idea and there's a lot of discussion about it, then more than likely it's one of the more popular ways of doing things.
If something is WRONG, be assured that folks would have picked up on issues and pointed them out, or just plain out said something is bad, or dangerous or not a good idea, you'd see it. We tend to police bad info pretty heavily.
If something is on here and people are doing it or talking about it, then it's a valid way....
You just have to decide which way seems best to you.
The design I linked lives up to it's name, it truly is a cheap and easy mash tun design...The "best?" It's the best for me....but it might not be the best for someone who went another route.