JTC has consistently been a better producer than Jost. In 4 less games, Compher had 6 more points last season and more goals. This year he has 3 more points in the same amount of games. Pacing puts that at a ~12 point difference over the season. It doesn't sound like a lot right now, but we are a ~quarter through the season. Then you look for outlier sort of impacts... Compher only has 2 multipoint games that both were 2 points this season... so 4 out of his 11. He has points in 7 other games. 9 our of 20 games he has a point. Jost also only has 2 multipoint games, but they account for 5 of his 8 points. He has points in 5 out of his 20 games. The difference offensively is pretty massive. You have a player that produces at a high end 3rd line/low end 2nd line rate (with level of play varying between the two lines fairly massively). Jost produces like a low end 3rd liner.
I don't buy the better forechecker, Jost is pretty terrible at 1v1 battles and when it comes to that, he struggles massively. Jost is better at breaking up plays with his stick and being in lanes. He's a better heady sort of defensive player and I think he is a better defensive player overall. Compher is better physically in the defensive zone, but I'd prefer him at wing because he isn't smart enough in lanes to be reliable enough when he gets pinned (and it plays to his speed advantage on breaking out).
Underlying numbers can really only go so far in evaluation. Compher is much better at creating higher danger shots and chances. He creates more off the rush and has more plays to the slot. That is where the offense comes from with Compher.