There are a few advantages that speak for 12.5 mm height in the 2.5” form factor. These drives are no longer handicapped by slower spindle speeds or outdated data densities. The latest Toshiba 1TB drive, the MK1059GSM, proved that it can beat the in-house 9.5 mm competitor, the MK6465GSX, on data transfer rates. Tests performed with comparable WD hard drives delivered similar results. In our particular case, the 12.5 mm Toshiba drive even "beats" its conventional brother in power requirements by consuming a similar amount of power, despite the larger amount of moving parts.
In addition to these performance results, the 12.5 mm drive provides clearly higher capacity related to the physical space it requires, and it delivers much higher capacity per watt. Looking at small form factor applications or even potential deployment of future 12.5 mm drives into server environments, it's very clear that 9.5 mm, two-platter drives might not make sense anymore.
However, there's still a catch. I/O and application performance for the 12.5 mm MK1059GSM are no match for the 9.5 mm MK6465GSX. This is key for drives that run your operating system and software. From our experience, we can tell that this isn’t a deficiency of the 12.5 mm drive, only a matter of firmware optimization. Apparently, the terabyte drive was trimmed to deliver maximum throughput with low power consumption. Access time and I/O performance were disregarded, which affects application performance. This performance characteristic is a great match for high-capacity portable storage, backup devices, PVR devices, and all sorts of compact multimedia products.
For now, we can make a clear recommendation: stay with 9.5 mm drives if you mainly care for performance. As soon as capacity is your primary focus, or if you want the best capacity per space or per watt, 12.5 mm products deliver more value, providing they physically fit.