On one hand you're negotiating with a regime that has already acquired nuclear weapons after breaking deals made by presidents of both parties but is basically contained geographically and can only commit nuisance acts (like having its missiles overfly Japan). On the other you're negotiating with a regime whose recent history is one of fighting proxy wars and attempting to exert regional dominance in a clash of religious ideology rivals which can turn into a "hot" war at any moment. It seems pretty clear that NK views nuclear weapons as far more key to its survival than does Iran, so it's not really surprising the negotiations won't be directly comparable with Iran more willing to deal away a pause in its nuclear development efforts in return for sanctions relief. If you look at deals (or potential deals) in terms of strictly "what does this do their nuclear weapon capability" it's easy to say the Iran deal will be "better." If you're looking in terms of regional stability and turning down the overall level of hostilities and risk of non-nuclear confrontation then NK might end up being the winner. There seems to be a window for a peace treaty to end the Korean War officially, some increased détente between North and South Korea, and other factors then the current efforts may be "better" long term. Trump gets basically zero credit for the SK-NK improved relations and other positive movement except for being recognized as a clown that neither NK nor SK wants to be the middleman, but if he gets "credit" for the mere act of being POTUS when a breakthrough happens then so be it. GHWB got credit for the Berlin Wall coming down when he had little/nothing to do with it but that's the way these things go sometimes.
