Representing a new generation of hybrid storage devices, the Seagate Momentus XT is quite an interesting product. Seagate has got rid of older problems that used to pester its previous series and now its 2.5-inch drive is indeed competitive to rather strong opponents. The Hitachi Travelstar 7K500 and Toshiba MKxx56GSY both showed high performance, so we cannot name an overall winner among them. You should base your choice on your usage scenarios.
The Seagate Momentus XT is a special case since it is not only a fast 2.5-inch HDD but also a hybrid device with 4 gigabyte of integrated flash memory. We guess this new generation of hybrid HDDs is better than their predecessors (we had a chance to check them out some time ago) because the effect of flash memory can be easily seen. But will this effect be called for? That’s a difficult question to answer. Modern OSes have advanced caching mechanisms while system memory doesn’t cost too much money. It is sad that the hybrid drive’s resources cannot be fully controlled by the OS. We guess it would be more useful than the total caching of everything as we can see now. Still, we are not inclined to disregard this technology as useless. The 4GB cache may be quite enough to make things go faster for some users, especially for notebook users with one HDD bay who just don’t have any other means to speed their disk subsystem up.
As for the comparison between full-size 3.5-inch and small 2.5-inch HDDs, there have been no fundamental changes. The large HDDs are still faster, both at sequential and random-address operations. Their advantage is not too large, however. So, if the dimensions or heat dissipation matter to you, you can consider 2.5-inch 7200RPM drives as a viable option. No one will dare call them slow.