Intel's move to a 1333MHz FSB is quite simply the next logical step. CPU core speed itself does make a difference to performance, but as we saw with Netburst it's not everything. Increasing bus speeds along with a new memory controller helps to make a difference, especially when you load the FSB up with too much data like the Core 2 Quad does.
Intel's current crop of quad core CPUs really are very hungry for bandwidth, and due to their weakness of two separate dies having to communicate across the old archaic protocol, this actually puts Intel behind AMD, especially when AMD puts its true quad core offering on the table (whenever that may be, your guess is as good as mine).
The 1333MHz FSB didn't make a huge impact on the Core 2 Duo as its core to core communication happens through the shared L2 cache, taking a lot of data load off the FSB and leaving it to feed the CPU its data rather than communicating between the two cores.
Core 2 Quad is simply not the greatest gaming processor, as its use of the FSB for core to core communications requires more cycles, and reduces the overall FSB rate as a result. If your intent is gaming only, a Core 2 Duo or Extreme dual core solution is more of what you are looking for.
Core 2 Quad's biggest strength is in pure mathematical operations, such as decoding, rendering and encoding, as well as media files and overall server style applications, making it the ideal digital media processor on the market. It managed to shave quite a few minutes off the Premiere Elements encode times as well as the overall score in World bench where CPU power is paramount.
Overall the Core 2 Quad and Core 2 Duo on the 1333MHz FSB will be the next big step, as Intel's pricing structure plans to make the 1333MHz series more financially viable than the 1066MHz counterparts, in turn pushing the P35 (and X38 when it hits the retail market) with a vengeance.
Our best advice is to use the new 1333MHz FSB CPU as there are no performance hits over the older 1066MHz versions, and with the increased bus speed the Core 2 Quad has much more breathing space to be able to perform to the best of its capabilities.