650b and 27.5" are the same wheel size. 650b is just the "French" sizing standard.
47c is just the tyre width in mm. So again much the same as 2.0" wide tyres. You could run any tyres from about 35 to 50+ mm wide on these wheels depending on your preference. If you are riding mainly on pavement, then you might lean toward slightly narrower tyres.

As for the bikes, there isn't going to be much in it at all between these brands. Having a local Cannondale dealer would probably swing it for me.