It greatly depends on the leather being compared to. There's a huge range in quality, and thickness, which impacts how it wears and breaks-in. I've owned BMW's with both leather and non-leather and the leather was considerably nicer than the non-leather, but it was in a much more expensive car (M5).
Most automotive "leather" is relatively thin, and heavily coated, to provide strength, prevent abrasive wear and provide an easy to clean surface. Leathers with thinner coatings feel more natural, but are prone to staining and require treatment (like the "Laguna leather" in my Jeep, that comes with a leather care kit).
A quality leather seat is like a good ball glove: it's a heavier leather that breaks in and becomes more supple. It's not slippery like vinyl or pleathers, but you won't find this in most cars advertised as having "leather" interiors or seating surfaces. The optional leather in my Jeep was a $7,000 option and it's nice, but it's not as nice as the leather in the M5.