Lazy answer is neither in particular. What the C's need is shooting and lots of it, especially with our style of play. If we were making our 3's this season, we'd be quite a bit above .500 I'd argue. I've been a Smart supporter since his rookie year, but he does not fit with Tatum and Brown and needs to be traded. I'm willing to keep Timelord because he's a good player on a very reasonable contract.
From the PG position we need someone that is willing to push the pace, make quick decisions, keep the ball moving, and hit the open 3. Can't have Tatum walking the ball up the floor throughout the game - leads to short shot clocks and stagnant offense. Schroder is obviously lightning quick but there are too many plays where he does not use his speed to his/the team's advantage and he is not a great playmaker. Need to move on from him.
From the "bigs" position we need versatility and shooting. Our lack of shooting from all of our bigs, including Horford, is absolutely killing us this season.
Who these players are and how they will be worked into our financial situation I do not know. But the flaws in our roster are glaringly simple. I am not willing to give up on the Tatum & Brown combo just yet - while neither are consistent playmakers, the game is also not easy for either of them because of a poor supporting cast. Too easy to load up the defense against both of them.