26" wheels give you a much wider choices of not only tyres but rims too.
Wider rims allowed says, a 25c tyres to feel more like a 28c without taking up the volume.
The other solution I can think of is converting your Fuji from 650c to 26", the major change you'd need to make beside the wheelsets is to purchase longer reach brakes.
Personally, the latter is the better solution in the long term, the smaller wheel (very slightly) allowed more room to fit bigger tyres in, and lowered the bottom bracket as low as a typical road bike too, especially if you plan to ride singlespeed indefinitely.
It also mean that you have two bicycles with identical wheels allowing you to not have two different option that may be expensive in the long term instead of having two set of inner tubes, just the one is enough.
26" wheels give you a much wider choices of not only tyres but rims too.
Wider rims allowed says, a 25c tyres to feel more like a 28c without taking up the volume.
The other solution I can think of is converting your Fuji from 650c to 26", the major change you'd need to make beside the wheelsets is to purchase longer reach brakes.
Personally, the latter is the better solution in the long term, the smaller wheel (very slightly) allowed more room to fit bigger tyres in, and lowered the bottom bracket as low as a typical road bike too, especially if you plan to ride singlespeed indefinitely.
It also mean that you have two bicycles with identical wheels allowing you to not have two different option that may be expensive in the long term instead of having two set of inner tubes, just the one is enough.