Read this to get an idea of why Spektrum limits the claimed range of the park flyer equipment:

http://www.spektrumrc.com/FAQ/tm.aspx?m=18

Basically, nitro planes typically have more conductive material in them (which can block the signal) than smaller electric park flyers, so the park flyers can get by with a single receiver, while the nitros have two or more Spektrum receivers (all "full-range" Spektrum receivers actually contain 2 or more receivers that are placed in different locations & orientations).

I'd use the 6100 in any electric aircraft that would be marketed as a park flyer. I use a 6100 this blue foam plane I built, and I fly it out almost as far as my .40 sized nitro planes without a problem (see photo below).