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The value perspective
Welcome to our famous value analysis, which adds capacity and pricing to the performance data we've explored over the preceding pages. We used Newegg prices to even the playing field for all the drives, and we didn't take mail-in rebates into account when performing our calculations.

First, we'll look at the all-important cost per gigabyte, which we've obtained using the amount of storage capacity accessible to users in Windows.

Even with the massive flooding in Thailand causing hard drive prices to skyrocket, SSDs remain an expensive proposition on a cost-per-gigabyte basis. The Momentus XT 750GB costs just 33 cents per gigabyte, while you'll pay more than a dollar per gig for the cheapest of the solid-state options we tested.

Our remaining value calculations use a single performance score that we've derived by comparing how each drive stacks up against a common baseline provided by the Momentus 5400.4. This index uses a subset of our performance data described on this page of our last SSD round-up. Some of the drives were actually slower than our baseline in a couple of the included tests, so we've fudged the numbers a little to prevent those results from messing up the overall picture.

Our overall performance index rates the Momentus XT 750GB higher than not only the Scorpio Black, but also its desktop Caviar cousin. The new hybrid also scores higher than the old Momentus XT, which sits 25 percentage points adrift. As you can see, though, the SSDs are in another class entirely.

Now, for the real magic. We can plot this overall score on one axis and each drive's cost per gigabyte on the other to create a scatter plot of performance per dollar per gigabyte. The plot gets a bit messy with all the SSD names included, so the solid-state drives are cloaked in gerbilesque anonymity. I've included the data points to illustrate the overall trend.

With better overall performance than its mechanical rivals, the Momentus XT 750GB sits atop the other inhabitants of the lower-left corner of our scatter plot. The drive's relatively high asking price hurts its value proposition somewhat, but the premium doesn't seem unjustified in light of the performance advantage the hybrid enjoys over the Scorpio Black. The SSDs deliver substantially better performance at a much higher cost per gigabyte, spreading the solid-state drives through the upper-right quadrant of the plot.

In general, there's a bigger difference between the performance of SSDs and drives with mechanical underpinnings than there is between the individual members of each camp. That said, the plot clearly illustrates that performance tends to vary much more between different SSD models than it does with mechanical drives and hybrids.

Although this analysis is helpful when evaluating drives on their own, what happens when we consider their cost in the context of a complete system? To find out, we've divided our overall performance score by the sum of our test system's components. Those parts total around $800, which also happens to be a reasonable price for a modern notebook.

With a suggested retail price of $245, the Momentus XT 750GB costs more than almost all of the 120-128GB SSDs we've tested. Solid-state drives offer a lot less storage capacity, of course, but this look at the numbers doesn't take gigabytes into account. Although they might be in the minority among notebook users, some folks simply won't need more than the 120GB of storage capacity provided by SSDs that cost less than the XT's asking price.