Keeping in mind that I've never seen either of these two models fly in person, I'd go with the Jantar. While the wing areas/spans/airfoils seem similar, the bigger versions of the Discus all like to fly fast and heavy. They'll probably be pretty close in performance, with the Jantar being more durable since the wing planform is simpler.

I know that the little 2m ASK-21 doesn't look like much (and after seeing a friend's 4m version, its hardly even close to scale), but it's a great little flier. One of the guys in our club had one, and he even used to toss it around like a hand launch on the flat field. If you did that with any of the other scale models in that size, you'd tipstall before you made the first turn! It would stay up in very light lift on the slope too, if I recall.

The 2m Fox is a great flier too, but it needs a bit of wind.