Here in Pennsylvania its great to have a portable upholstery machine when it gets cold and messy outside. I know Tucson can get chilly in the winter, but not like here!
That said, when you have those "upholstery only" jobs, a light, easy to set up unit can be nice.
Here's my thoughts: Spotting units have too little solution and recovery capacity to do more than a chair. And if you start cleaning delicate fabrics, most of the safer, neutral to acidic preconditioners foam like heck. You'll be replacing vacuum motors alot, Jim.
If you need a small unit, and you want to use both water AND dry cleaning solvent, the Kleenrite and US Products wet and dry cleaning units are both good choices. My problem with them (and yes, I sell one of the two), is that they don't really have enough vacuum for good extraction and drying, in my opinion.
There are small portable "wet clean only" units, such as the Kleenrite Sphere, Cleanmaster Rexx, and a myriad of other brands that have 3 or 4 gallon capacity, 100 PSI pumps, and three stage vacuums, as well as heat. These units have enough pressure and vacuum to prosperly utilize a dry tool, and also to give you good extraction and heat.
There should be little reason to dry clean fabrics if you have a dry tool, some neutral cleaners, and a couple of different dye setting agents.