1. Durability
2. Classic look
3. Very comfortable for many people (mostly the wider ones like B17 and B68 models)

I had one for over 25 years, and it could have been good for another 25. Certain models are almost a guaranteed comfort, but it's usually the wider ones, as they feel like benches or barstools; the slender models like the Swift and the Swallow seem to be a hit-and-miss for various people. You'll also note that many people here do not like them for their hardness, but the barstool down at St. Stephen's Pub is pretty hard, too, and I find myself able to sit on it for hours . Other people find that the Brooks saddles require too much care, but to some people that little bit of extra care is the thing that makes it special, as if the Brooks is a living element on the bike.

You'll have to read more about it (with a search), and come to your own conclusion.

Good luck.