Originally Posted by ShortLegCyclist

Wider tires can handle more riding surfaces... with 25's you are not going to want to take those bikes on gravel, but if you could mount 28's or better 32's or 35's you could.

There was a widespread belief than thinner tires roll faster but it turns out that is probably not the case, going to 28's loses little to no speed and gains a lot in ride quality, depending on the tire used (the more puncture resistant, the less comfortable and fast the tire will be in general).

If you ever want to ride these in the wet, the ability to mount wider tires also directly translates into the ability to mount fenders. If you have no clearance with 25's mounted, you will not be able to mount full fenders, let alone wider tires.