Do we need a wing? Absolutely. But I'd much rather draft a big man.
The first question is, will there be a good big man available when we draft? I think it is extremely likely. Keep in mind, last year two of the top five draft picks were spent on European big men, and most people (including me) haven't even looked at Europe yet. I don't want another 19 year old rookie unless it's a phenom type like Irving or He-Who-Shall-Not-Be-Named. And that's a major part of the equation. If we want to maximize the Irving Window, to steal a term from somewhere else, now is the time to get older rookies and younger vets who can play together.
That leads into the second question- we clearly need both a big man and a wing.Luckily, we need have both quite a bit of money and a good draft pick. Are we better off spending a draft pick on a wing and getting a big man in free agency, or a big man in the draft and a wing in free agency?
Part of that can be seen in our roster. At guard, we have Irving, Sessions, Parker, Boobie, and Gee. The dropoff from Irving-Parker to Sessions-Gee is almost nonexistent, and we still have Boobie. On the other hand, after Varejao, Jamison, and Tigger, we have...Erden? Samuels? Hollins? Harangody? The dropoff in big men is huge, and for guards it's a lot lower.
That gets me to the second point. Would you rather get a Wilson Chandler or Aaron Affalo type in free agency, or a Glen Davis type? Only two power forwards in the top 40 free agents last year changed teams, and they were Glen Davis and David West. For Centers, there were three- Tyson Chandler, Samuel Dalembert, and Kwame Brown. Pretty slim pickings in free agency. Seven shooting guards in the top 40 changed teams. Competition is much higher for good big men in free agency.
So, do we actually need three good big men? Heck yes. Most big men go 36 minutes in the playoffs or less. This means your third big man can get almost as much time as the first two. Sometimes it seems like the big man off the bench is actually more important, as he can support his teammates on both offense and defense.
In short, we need both, but a big guy will be easier to get in the draft and be better for us, both in the short and in the long run.