I like both of them... but AM is all about the wizards, in very much the same way that Pendragon is all about the knights.
They're not the same niche... but both are excellent.
Well, the thing is, and what I was trying to get at, is that Ars Magica doesn't _have_ to be all about the wizards.
When we played our saga, our group had fully adopted the troupe-playstyle, so every player had two main characters, a magus and a companion, and a couple of grogs (although the latter were more or less shared by the players).
We also had rotating storytellers, each focusing on a different aspect of the campaign. And since two players had knights as companion characters, we had quite a few sessions of stories that focused on them. In fact one of the players had designed his Magus as a Verditius that was more or less a court mage for his knight character, working in the background to enchant his equipment, and not really doing much else.
If you have the 'Lords of Men' supplement for Ars Magica 5th edition, you almost have everything you need for a campaign focused on chivalry.
Likewise you could play a campaign focused on the Church, or on Merchant Houses, or on the Supernatural, e.g. Faerie Courts.
So, comparing this to Pendragon, I'm not sure if the reverse would work as well: While Pendragon has some rules for playing Magus-type characters, I'm not sure if it would work to make them the focus of a campaign. I might be wrong, though, since I never bought as many supplements for it as I did for Ars Magica. But I had the impression it was pretty much expected that evrey campaign focused on the knights.
What I like about both games is that they have a scope that goes beyond a group of characters. Both have great downtime systems. In Pendragon, you care about raising a family to continue your legacy, and in Ars Magica, there's the Convenant where most of the characters live, that remains a constant as generations of Magi and their companions come and go.