I’m in the opposite position to the OP. I’ve got a vaya with 700c wheels and was wondering whether to get a set of 650b ones :).
I do already have a second set of 700c wheels which are currently on my Kaffenback and these are actually my best set (hand built by Malcolm at the CycleClinic). I have swopped them over before, however the Kaff is only a 9 speed set up so I also need to put a 10sp on when moving these to the vaya. If I put bigger tyres on the good wheels when on the Vaya, I have to swap them back for narrower ones when I use the Kaff, so it’s all a bit of a pain.
I could simplify things by making the Kaff 10spd (or making the Vaya 9spd) or just not use the Kaff…or buy a cheap set ..or…
AS you can tell. I can’t make decisions.