Altra's Superior 3.5 doesn't really differ too much from their previous version with regards to support and arch type. Really the most noticeable changes are on the exterior of the shoe's upper. You'll notice the addition of securing points for the brand's trail gaiters, located on the sides. Other than that, the revisions to the shoe are minimal with regards to changes in overall support. As a user of the 3.0, I will probably wait to see what they do with the 4.0, if there is one, before upgrading to a newer version of the Superior.
To answer your question, the Superior tends to be more suited for neutral pronation and arches. The Superior line is a great one, so I would suggest picking up a pair of insoles to support your particular arch type.
So in short, Altra's Superior 3.5 is a neutral trail runner.