The only functional difference is in how the wing is joined. The Avistar Select RTF (with engine and radio) uses a metal rod with a couple of screws/bolts for quick wing assembly. The ARF version of the plane uses the more traditional wooden joiner and epoxy method.

The ARF design is actually considered the better of the two. The wooden joiner is lighter weight than the metal rod in the RTF, and using 30-minute epoxy to join the two wing halves as described in the ARF directions will provide a very solid, durable joint for the life of the plane.

The RTF method for joining the wings may not last as long. Vibrations from flying and/or just running the glow engine can slowly work open/expand the screw holes that are used to secure the wing halves together, thereby causing "play" or movement in the joint. This could eventually lead to wing failure over time if not caught and repaired.