you can play everything with a JS, not so much with the jem. I have/had different models of both and the jem is not an axe you would want to play a more chordal music with, its neck is too wide.
the js is like a
super strat, you can play anything with it, its pickups are great for everything.
that said, i'd take a good ol' gretsch for country over any of the above
