Full disclosure: As you can tell from my username, I'm a big Spooner fan.
When Krejci's hip implodes in the next 2-3 years and Bergeron finally starts to slow down offensively, who are we counting on to pick up the slack? Just JFK and Donato? Maybe Czarnik? I'm sorry, but I'm not comfortable betting on 2 prospects + Czarnik. Czarnik will never be better than a 3rd line, energy / PK guy. He's got wheels but he does not have the offensive IQ to make it happen in the NHL if you ask me.
Keep Spooner. He has the speed, hands, and vision to be a very good #2 center in the NHL. Faceoffs, as others have mentioned, really do not matter very much by any statistical measure. I think choosing a guy who can win faceoffs over a guy who can set up and scores goals is dumb. Moreover, Spooner can get better in his own zone, on the back-check, and in the corners - you can coach those things much more easily than you can the offensive stuff he already brings to the table. He's not perfect, and probably never will be in those defensive/"battle" categories, but if he can be at least competent than I think it's more than worth keeping him around for the 40-50 points a season he can provide. That's not even considering his potential to put up closer to 60. I agree with the comparisons to Savard - except he's even faster/more agile than Savard ever was.
Spooner has the ability to be a game-breaker. We've seen it the last few games - he can just take the puck and within seconds manufacture a breakaway or a serious scoring chance. If you can keep a guy like that for under 3 million, you would be absolutely foolish to not do so. We're paying Beleskey more than that to do much less. Even at his best, Beleskey has never put up more points than Spooner did last year. Hitting guys and looking like you're trying hard doesn't win games - making goals happen does.
Give Spooner the chance to play with Vatrano for the rest of the year and watch those two finally give us a 3rd line that does more than dump'n chase and get scored on. You'll be amazed at what that does for our playoff chances.