650B wheels are NOT an "alternative" to 700C wheels, unless you know you will always want to ride on wide pillowy tires and you know you will never want to ride that bike fast. They end up pretty much the same overall diameter as 700c with narrow tires anyway, so you don't really gain anything if you're a short person - at least not if that's your reason for going 650B. You would need 650c for that, or 26 inch mtn bike sized wheels.

Why some people are promoting 650B is beyond my understanding. We've been through all the sizes over the decades of the 20th century. We came to where we are because it was practical, and I see no reason for anyone to still be monkeying around with returns to obsolete wheel sizes, nor for anyone to buy one unless they just have too much money to spend on frivolities. It's one of those minor fashions that wouldn't exist without the internet, I think, like fixed gear bikes.