He's better if his responsibilities are mainly attacking, but not in an advanced position, and certainly not as a number 10. I see it this way:
Anderson: strength, a lovely burst of acceleration into space, an eye for a gamble, whether in the form of a through ball or an extended dribble, can beat a man if there's space available, good long passer. Somewhat erratic control, and a tendency to take the risky option too often.
Cleverley: tight close control, can maintain possession and use the ball when closely marked, not a dribbler per se, but excellent at escaping pressure with a bit of footwork in a tight space, rarely loses the ball, good short passer. No real pace or acceleration, and a tendency to take the safe option too often.
They're both best when their defensive responsibilities are reduced by someone like Carrick. But Cleverley's close control and consistency mean he's very good on the edge of the opposition box, where he can keep a move going under pressure from defenders, and make use of his lovely one-touch short passing. if he sits too deep, his 'safe' passing stops being a positive and becomes a negative, slowing the momentum of our attacks.
Meanwhile Anderson is best starting deeper and running into the space, so as to be able to use his burst of acceleration to beat a man, his long passing and eye for the through ball (or pass out wide) to send someone in behind the defence before they form up. His slightly inconsistent first touch and the fact that he dribbles best with a bit of room rather than in tight spaces also lend themselves to a deeper starting position. His 'hollywood' tendency is suited to a deeper position, where things are more likely to come off. Starting too high up the pitch, he'd just lose the ball a lot.
Basically, it's a Toure/Nasri situation. One needs to drive from deep, the other to tiki-taka closer to the goal. Both benefit from Carrick's presence. As a 3-man midfield they are wonderfully balanced. I say start them all together.