We still have 3 pretty good attackers in Matri, Quag and vucinic add another promising attacker for cheap and we'd be set for next season.
On the other hand, we NEED quality CB, LB, a couple of backup CM and quality wingers.
We aren't getting Damiao this winter, this is for next season I believe. According to rumors we will be looking for a CB & CM this winter. That leaves a LB and not need for wingers when it makes much more sense to use the 433. We have better players for that formation and would be too costly to by the 2 wingers to take us AND the 424 to a higher level.
For example: Regardless of formation we still need a CM, CB, LB...well, 2 of those should be brough in winter according to the rumors...that leaves the LB for next summer with a quality striker. Quag is good, but IMO if CL we need someone better and Quag for depth.
As opposed to buying a CB, LB, CM, RM, LM for the 424, its easier to buy a CB, LB, CM, ST for the 433.