Just a thought. I always see people putting down Harry Potter-style magic and calling it weak and other stuff like that. While it is not as flashy or DBZ-style-blow-stuff-up poweful as in MSN, it is quite powerful in its own right.
I will grant that it is not as combat specialized as Negima-style magic. I think of Potter-magic as being more subtle in nature. Not to mention more versatile. I mean those little wands are easily concealable and spells can be let off with a single word and gesture, rather than the long(er) chants used by Negi and co. Plus, Wizard magic seems more geared toward replacing technology in everyday life wheras Negima Magisters are more integrated with the modern world.
Plus, I don't see Negi and company apparating, totally paralyzing their opponents, turning invisible, or any of the other impressive feats detailed in the Harry Potter Books. On top of that, Potter-Magic doesn't seem to wipe out its users as much as Negima magic does its.
If people are worried about Negi and Harry interacting, how about Negi takes Harry under his wing? Or, in his mad rush to avoid the Hogwarts letters (First Book) Vernon Dursley ends up in Wales and Harry meets Negi before he graduates?
Just a few ideas.