You always ALWAYS want to trade UP. Depth doesn't mean ****, because great free agents always show themselves over the season. Most seasons I have trouble figuring out who to drop because I want to keep ALL my players...so I try to trade to get a better star, giving room to add more good players to my roster.
DEPTH = NOTHING in fantasy, unless they are high caliber players you would NEVER drop when healthy.
Depth would be like
KG for Richard jefferson and Kirk Hinrich. This would be a good trade if one team needed a star and the other depth. THIS is depth.