The Continental Schools give upon talking exactly in order to say something relevant about one's inner mental states. But can say nothing true about the external world.

I suggest that to see what it is about the Kant Friesian School that is so great  it is helpful to compare it to Husserl. With Husserl we see he was trying to put a person into a sieve. That is to sieve out all the predicates that do not belong to a man per se. By that he hoped to find he essential mental states that make a man into a man and thus to create his method of Phenomenology. And thus comes to true and sure knowledge. [A very ambitious project, which is highly circular.] 

To see and understand just what he was up to helps to see the advantage of Leonard Nelson. who realized that knowledge has to start with axioms. Not mental states. The is the regress of reasons. You have got to start somewhere. And that somewhere can not be just mental because that says nothing.(Nothing by itself.) And that somewhere can not by the senses because they also say nothing at all. But you can not put these two together to make something sure and certain because then all you have got is nothing plus nothing. You have got to start with Immediate non intuitive knowledge.

I hope that is clear enough. And I admit I am on the side of Nelson for a another reason. That is the Nelson Affair file in the drawer of David Hilbert.

But here I also wanted to add another point which I believe is very important. There is something about the Leonard Nelson School [Kant-Fries] that deals with the very areas where the Continental and English Schools [Analytic] fail. The English Schools start with the external world and insist on talking exactly. Well they talk exactly but can say nothing coherent about the Inner World. {My mind is not just a jumble of sensations. I have got this news to report to them.} The Continental Schools give upon talking exactly in order to say something relevant about one's inner mental states. But can say nothing true about the external world.  

So you can see what it is about Leonard Nelson that gets both right and once you get into it, it is impossible not to be impressed. [See the web site of Dr Kelley Ross.]