Hi I've had a pair of Ns1000m's but not the 4412's I have however owned several Jbl's (4311's, L110's, L65's, and 4343's).
The yammies were detailed, clean and quite neutral. The were well suited to acoustic, and not as great for rock for example. They were quite revealing of the source, so when I streamed lower quality digital files through them they sounded not so great, but were great with really high quality flacs. They are sensitive to placement especially with regards to bass. You need to experiment with height and distance from walls, otherwise you'll find them a bit bass shy.
As I said, I've not had the 4412's though I've heard good things about them. I listen to a lot of 70's rock which I think is bit better suited to nice jbl's I've found. So comparing my 4311's side by side to the yammies, the yammies would win on detail but the punchiness of the 4311's just sounded better with rock etc.
The yammies are excellent particularly if your'e more into acoustic stuff. I do prefer my 4343's over the ns1000m's for sure though.