Back when I was a little older than the "target audience," I discovered the "Young Wizards" series, and it really caught my imagination. My opinion of it gradually declined as I matured, because I came to realize the dubious quality of a series about "kids like you" performing magic, and especially as later volumes focused so much on the "YA"/teenage-angst/relationship side of the story at the expense of the worldbuilding and the nominal plot. But I still think that the more SF approach to fantasy (it's science fiction, with the allowed one speculation being this magic system, which is described in scientific terms).
The Harry Potter series stands in great contrast, by the way. While it is far more evocative to the population as a whole, my opinion of it fell at a far younger age and far faster, and because
- it became increasingly obvious that she was at the eleventh hour deciding to ret-con an utterly implausible set of romantic pairings and insist that what seemed to me to have been telegraphed obviously from the first book on had actually never been there,
- the tone of the series kept getting darker and darker without any hint of real eucatastrophe (in the end Harry literally comes back from the dead and we get status quo ante bellum, eugenics reduced back from official policy only as far as being the unspoken opinion of the still-dominant political faction), and
- the holes, inconsistencies, and contradictions in the worldbuilding became egregiously obvious.
I now value Rowling's work highly as a base on which many fan authors have built work that is far
better except for needing her original to make sense.
As far as similarities: Really, there's not much. They're both "YA fantasy," depicting teenagers doing (different sorts of) magic while (supposedly) growing up, but beyond that I really can't think of anything.
(Oh, and if anyone liked the Young Wizards universe at all, there's two very delightful non-YA side stories whose protagonists and POV characters are cats,
The Book of Night With Moon and
To Visit the Queen.
I don't know why Harry Potter was so much more commercially successful and widely popular than the Young Wizards series; I suspect that there was some factor of "right place at the right time," but I'm convinced that part of it was that the publisher(s) decided that
Harry Potter and the Sorcerer's Stone was
going to be a hit and spent a lot of money on a marketing campaign to make that happen. And the Harry Potter series was published by Scholastic in the U.S., which has one significant advantage that few other publishers in the country have: it sells directly to schoolchildren via school book sales (some small part of the profits of which are shared with the library of the school hosting them, adding an incentive for parents to sponsor children's purchases) and "book club" catalogs distributed by elementary-school teachers.
Part of it may also be that while Harry Potter is in a "magic school," for the most part that's just the backdrop of the story, and his success doesn't depend principally upon whether he learned what he was supposed to well enough; he just forces enough power through, or survives by luck, or obtains some magical MacGuffin; for children who had previously apparently despised reading, let alone any other sort of academic effort, that's more of a "wish fulfillment fantasy" than having to learn to speak a whole new language in one's free time, memorize a long saga while transformed into a whale, or whatever else Kit and Nita had to do.