I know nothing about Lion & Dragon, other than that it's by Pundit, but I've been an Ars Magica fan on and off for quite some time. So I don't know whether L&D is the game you want, but Ars Magica almost certainly isn't. It tends to run pretty heavily towards the higher end of the crunch spectrum and the magi start out substantially more powerful than the other characters[1], and they only go up (and up... and up...) from there. As in, a sufficiently-old Flambeau (the fire specialist house) magus could plausibly make up a spell on the spot which would cause the entire city of Paris to simultaneously burst into flames. (In the course of a typical campaign, the PCs are unlikely to get that powerful, though. They'd have to actually invent and learn the spell instead of making it up on the fly.)
Another game in similar vein that you might want to take a look at is Kevin Crawford's recently-released
Wolves of God, which should fit on both low-crunch and rare-magic, although it may be too England-centric and assumes that PCs are generally cooperative with the church rather than opposed to it.
[1] As mentioned in an earlier comment, that's a core design point - characters are deliberately divided into "magi", "companions", and "grogs" with each category less powerful than the one before, which is balanced by having each player make characters of all three categories and then switch off between their characters from one adventure to the next.