I'd pick Gallinari. He's more rounded than chandler.

I'd probably go with Chandler, for an odd reasoning:

I think Gallinari is the better player, but I envision him being much more likely to get overpaid, while I think Chandler is more likely to be able to be signed for a salary that is fair to his value. I think Gallo is a great shooter, but can't defend the 3 and can't rebound/defend the 4 (so a poor man's bargnani) but will, due to the size and range, be signed like he is a key starter. I think Chandler will be able to be signed as if he's a 6th man/5th starter, and that is where I see his role.

Edit: basically, I could see someone offering 8-9 mil per year to start Gallo at the 3 or 4 then have to cover his rebounding/defensive deficiencies, while I could see Chandler making 4-5 being a 6th man/ glue guy starter that can play D.

Not certain enough about Gallinari's ceiling ... so I'll take Chandler because I think he's a better two way player.

If I am the Knicks and looking for someone to complement Carmelo Anthony on the wing, I definitely take Chandler because he is able to defend the two spot and take some pressure of Melo defensively.

Because Rondo is on this team, I'll take Gallo. A little more polish to his game, he can be a regular 20ppg scorer.

Like someone said, Chandler now, Gallo for the future. I think Chandler is performing well in his contract year. I dont think his numbers will be as good next year... Gallo's knock is that hes incredibly inconsistent. One night he'll go for thirty and they next he'll go for 8 or 9.

I think Gallinari is a 3, not a 4.  Yeah, the knicks have played him at the 4, but he's a 3, so people shouldn't be weighing in on his value as if he might play some 4.  That's like considering Garnett a 5.

Gallinari can shoot really well and he is surprisingly athletic too.  As for his rebounding, he averages 4.8 rpg, which is right up with Paul Pierce and his 5.0, so he's a perfectly fine rebounder for a 3.  I think a ceiling for Gallo on his prime is to be a player similar to Peja Stojakovic in his prime and I don't think its too much of a stretch to say that he will reach that given what we've seen from him so far at so young.  That's a much better player than Chandler will ever be.  I do like Chandler a lot, but I'd take Gallinari.

This surprised me, so I decided to take it on and compare Gallo and Pierce as rebounders with better metrics than raw rebounds per game.  Rebounds per game is flawed as a stat because it doesn't account for certain variables like minutes played and rebounding opportunities.  For that reason, I prefer rebounding percentage, which simply determines the number of rebounds taken by the player in question out of the number of available rebounds.  It negates variables such as minutes played and the team's pace.

This year, Pierce pulls down an awful 1.3% on offense, along with a very good 15.7% of the boards on defense to give him an overall rebound rate of 8.9%.  Gallinari is better on the offensive boards at 3.2%, but he's significantly worse on the boards defensively at 12.3%.  His overall percentage is 7.7%. 

For kicks, I got Chandler's rates as well - 4.0/15.5/9.7.  Wilson Chandler is above average for a SF on the boards.  Pierce is perhaps a shade above average this year, and Gallo is a shade below.  All of these stats were pulled from www.basketball-reference.com.

To return to the actual argument at hand, I'd take Chandler over Gallinari.  He lacks some of the offensive potential that Gallo has, but he's much better on the other side of the ball.  With Chandler you can ask him to defend multiple positions and expect him to hold his own; with Gallo that's not the case.  Also, keep in mind that Gallinari isn't the only one with potential here - Chandler has a lot of room to grow, too.

Gallinari
You can teach him or make him work on his weaknesses.  His strengths I simply don't see Wilson attaining that level of offensive skill.  Gallinari at the least boxes his man out and plays good team defense (scal like) than that would be fine by me.  Yes no one boxes out.  I think its easier to replace Wilson's overall game than Gallinaris offensive game and potential to be great.