Why is Mx0 getting brought into this, anyway? Besides the magic school thing the series are totally different types of shounen, it would be closer to compare Mx0 with Kaiji and Negima! with Naruto or a Jump property.
That said, Negima! is on average a very above average series. Akamatsu's fanservice is quite good and he's got enough ideas to supply anon with many faps long into the night. The story is decent, but improves all the time.
I actually liked the first six or so volumes, even with the harem stuff, but I hated the Mahora Festival after the Takahata fight. Everything just got so repetitive and boring, god and that shit draaaaaaged.
But right now, Negima! has the most interesting arc of all current manga. Nothing else right now can touch it.