I'd say poni will be a solid third liner who scores 15-20 goals a year. But that said Antropov will get you more goals and many more assists in the future than poni if he can stay healthy. So i take Nik.
If you were just asking me as a GM of another team - "who would I rather have ?"
The answer is a resounding "ANTROPOV!"
Antropov potential is much greater than Ponikarovsky's.
In fact, as much heat as I might get for this - Antropov's potential is greater than or at the worst equal to (possibly, possibly Steen) any of the current Leaf young forwards/prospect. Of course, Antropov is also the most fragile one of the group - so that detracts a bit from his value as a player.
Of course, if you were talking about who it would make more sense to deal; then logically Antropov would comandeer more on the trade market, even if I were reluctant to trade him. However, I'm not really sure if Antropov's trade value is close to it's peak right now. Antropov of this season (so far) isn't going to get the same return as Antropov at the end of last year.
Antropov has more upside for sure, but I think his upside will never be reached because of his injury issues. He needs to play a physical game to leverage his physical assets; otherwise his development is stunted. But he keeps getting injured when he plays physical.
I do not think he will ever be a consistent performer. If I can dangle him for a very good D man then I do it - as long as the other team's GM still has stars in his eyes when he sees Nic. Then the Leafs get a good deal in return.
Keep Poni because he will not fetch as much as a star-crossed GM will pay for Nic.
A surprisingly good question, given the clear superiority of Antropov's skill level.
On the other hand Poni has produced as much offense as Antropov this year and it is difficult to predict if he will continue to progress or whether or not we have already seen the best he can do. On the other hand Antropov also may or may not reach his potential, even if he stays healthy. On the other hand (yeah, that's three hands) Poni has a more consistent approach to the game and doesn't hang around the edges so much.