The "resolution" numbers you're seeing are a red herring. The quoted number is the height of a layer that the settings shipped with the printer are good for, not the precision or accuracy of the print head. The X, Y, and Z resolution, as well as the extruder step size on a Solidoodle (and almost any other printer these days) is plenty good to print .1mm layers. The challenge in printing .1mm layers is that you're depositing a very tiny amount of plastic onto each layer, so variation like filament quality and moisture, temperature, and speed matters a lot more.

Check out RichRap trying out different "resolutions" (layer heights) on his MendelMax printer with a Wade's extruder here to learn more about how layer heights work:

http://richrap.blogspot.com/2012/01/slic3r-is-nicer-part-3-h...

I have seen on the Solidoodle forums that the Solidoodle has a .1 "mode" but I don't have the specifics. The Solidoodle website says, "It's possible to print hi-resolution parts at a layer height of .1mm, which gives top-notch looking prints".

> Can they both use the same filament?

If you get the heated bed option, yes.