While the heat sink and fan of the 7528 are considerably larger than those of the 6228, you'd be sorely mistaken to believe that more is better in this instance.
The 7528 is somewhat more silent due to its 70 fan, which spins more slowly.
But the fan is too weak to blow the heat out of the heat sink. The difference isn't dramatic, but it is measurable. In light of this, we don't recommend the 7528 for overclocking.