I used to have a Contender, and am contemplating getting another to set up as a light-weight rifle and hunting handgun. I am not interested in the Encore. Is there enough difference between the original and the G-2 Contenders to justify one over the other?

It's mostly personal preference. The old Contenders are a smidgen smaller and lighter if you are going for absolute size and light weight. Some say they have a better trigger. The G2s main advantage is not having to reset the action if you let the hammer down without firing and in factory configuration is a better geometry for scoped rifle shooting. The buttstocks and hand grips do not interchange but barrels and forends etc do interchange.

There are few carbines more compact and lighter than an old contender with the factory plastic stock set and a 16" tapered barrel at a smidgen over 4 lbs with iron sights. I prefer the size and weight of a scoped G2 with wood stock set and 23" or longer bull barrel.