I haven't tried the N3 for a long time to make a comparison, but I was looking at the M7 to replace my Z5 - the M7 was a really nice fit and sounded good, but as decent as the bass is, I think I am accustomed to a hybrid and prefer dynamic bass. There is a lot of appreciation for the N3 with an upgrade cable, some prefer it to the ex-flagship Z5. I feel that Sony has come in with quite high pricing for these 3 recent releases, I'm not saying that they aren't value for money, but the price difference between the N3 and M7 may not equal the difference in enjoyment.
I sold my XBA-Z5 because they were a nightmare fit for my ears and found a worthy replacement, but I am keeping an eye out for a cheap secondhand N3 as a everyday secondary iem - I've always enjoyed the classic Sony dynamic sound.