I prefer low magic for essentially mechanical reasons: as a player or a GM, I hatehatehatehate D&D magic because of what it does to the gameplay. I don't mean the wish, scry/buff/teleport or polymorph game-breaking elements, I mean the way every spellcaster slows down play.
A human fighter will have at most 19 feats at 20th level, most of which are passive (allowing him to take actions without an AoO, applying a bonus to weapon attacks with the weapon he basically always uses, allowing him to use his Dex bonus to attack, etc.) and none of which will take up more than one or two paragraphs in the PHB.
A sorcerer will know 43 spells at 20th level. At 1st level, he'll know 6 spells to the human fighter's 3 feats. Wizards, and especially clerics and druids, will know easily twice that many, and in the latter cases quickly go into the 100s with additional books.
Spells take up about 1/3 of the Player's Handbook. The mere lists of spells by level occupy more space (16 pages rather than 10) than the races. The longest spell descriptions occupy an entire page.
Barring a player with a photographic memory, this ludicrous amount of (oft-overlapping) spells bogs down the game beyond imagining.
I have no problem dealing with 3-base class, 3-PrC characters who made class choices to maximize their number of feats in certain critical trees - they'll still be a dozen or more spells shy of even a single-classed Sorcerer, the least egregious core spellslinger. And considering the relative simplicity of feats, a player has a better chance of memorizing 30 feats than he would 30 spells.