I've used the mini for 10 years with everything from the sanders to the Kapex via the OF1400. Most of the time I only know to change the bag when the hoover weighs a ton, the bags last me months. I do have three other Festool hoovers now, one for the Planex, the CT36 in the workshop and the CT-SYS for site sanding and general small cleanup, but the mini is the first call for site stuff.
It's small size has only ever caused a problem when it's running with a sander in a hot room and it has to cool down after a hour or so. I have to consider the weight when full with the larger hoovers, especially in small victorian properties with narrow hallways and lots of stairs, you might not see that as an issue. In terms of suction I think there's no difference.
If you are using it with the saws and routers in inhabited domestic properties and you want 98% dust extraction you might want to stick with the CT26.