ArtRage Wacom edition is an 'OEM' edition of ArtRage 2.5 Full edition. The only main difference is the branding - the tools and features are the same as ArtRage 2.5 Full edition. You cannot purchase ArtRage Wacom edition as a separate purchase - it comes bundled with a Wacom tablet in Europe.
ArtRage UltraMobile edition is for people with Ultra Mobile PC devices - handheld PCs with a typically lower screen resolution than a notebook or desktop computer. The ArtRage UI has been changed to accommodate the smaller screens.
So the only versions you should be looking at are ArtRage 2.5 Full edition, and ArtRage 2.5 Plus edition.
ArtRage 2.5 Plus edition has the same feature-set as ArtRage 2.5 Full edition. However ArtRage Plus edition comes with a CD and printed manual in an attractive DVD case. The CD also has additional content - stencils, tutorials, demonstration movies.
AndyRage's mantra for graphics engine code:
"Sure - how hard can it be?"