One advantage of a 650B conversion--versus riding a native 26"-wheeled bike that's not a racing MTB--is that you can really improve the ride of an 80s racing-oriented bike. You get the advantage of relatively light weight and likely somewhat steep frame angles, but soften out what is usually a harsh ride on 25mm tires by opting for 38mm x 584mm tires. My best example of that in the fleet is a 2001 Lemond Zurich with 853 tubing. With 38mm tires (the Pacenti version can usually be found for not too much $), it's a lightweight all-rounder.
IMG_1236