Examine the key differences between the Iranian and North Korean nuclear programs. Why is that US could have a diplomatic breakthrough with Iran but such a breakthrough with North Korea appears to be far away?

Comparison has been drawn between Iran and North Korea over their nuclear programs and the international efforts to curb them. 
There exists key difference between the two nations with regard to their nuclear programs:
a) Goals: Iran has always ruled out the production and pursuing of nuclear bombs and nuclear weapons while N.Korea aims to produce nuclear bombs and already has nuclear weapons in ts arsenal.
b)Technological Capabilities: Iran only had ability to enrich Uranium . N.Korea has ability to produce dozens of nuclear bombs and has acquired and developed sophisticated nuclear technology.
c)Engagement with International Entities: Iran had allowed access to officials of International Atomic Energy Agency to visit Iranian fuel nuclear reactor while N.Korea has not allowed them since 2002.
US and other European nations have signed Joint Comprehensive Action plan with Iran lifting some of the sanctions. This breakthrough has been possible because:
a)Political regime in Iran was more keen to unlock Iran’s economic potential limited by sanctions. Smooth political transitions allowed for election of leaders who wanted to engage with world  powers unlike N.Korea where power is firmly held in hands of one family.
b)Iranian economy is integrated into global economy and depends on international trade while N.Korea has been an isolated state.
c)Sanctions had made the people suffer which put pressure on political class which is partially elected in Iran unlike N.Korea which completely dictatorial and ruthless state.
d) Due to proximity of Iran to Europe, European nations were more keen on resolving the nuclear proliferation issue with Iran and prevent it from acquiring any weapons rather than N. Korea which is geographically distant hence strategically less important.
e) A breakthrough could be reached, as Iran was ready for negotiation while in case of N. Korea, it has shown no interest in negotiation.
Thus a combination of political, economic and technological factors differentiate the approach of two nations and international community in dealing with them. A diplomatic breakthrough is the only way to diffuse the crisis in Korean peninsula.