I have passed JLPT N1 years ago. As a non-native speaker of English, I have also taken TOFEL. In my opinion, the two tests differ with each other in term of their orientations. JLPT evaluates its test takers in terms of their passive language skills (listening, grammar, and reading.) In another word, they want to know how well you know the language. This is especially the case with the grammar section of N1 which includes a number of expressions not commonly seen in daily life. It's more like a quiz than a test.

TOEFL, on the other hand, evaluates its test takers in terms of both their passive and active skills. In another word, they want to test how well you could use the language. Many of the tasks included in the test set themselves against the college life in U.S. It is mean to equip its test takes with the language skill to survive in a foreign country where English is spoken as a first language. So it's more like a training program.

If the native speakers are allowed to take the tests, my speculation would be they would view TOEFL easier than JLPT as its content is more close to daily life and actual language use than JLPT.

I think JLPT N1 is most of the time they are for business and some words and phrases we seldom use. Furthermore, the exam is quite difficult.  However, if you pass it, it means your level is as native level. 

Most of words and phrases in N2 are used in normal conversation. If you live in Japan, it is enough for you. You can talk with native speakers.  Between N1 and N2 are very different. Some natives made mistakes when they tried it because some grammar are their first time.