• Definitely speed. A mobile device equipped with a SSD will almost always outperform one with a hard disk. RuggedPCReview.com's benchmark testing has proved that over and over again.

• Smaller size. SSDs also facilitate smaller, lighter devices. That's a one-way street, of course, as an SSD will fit into a device designed to accommodate a hard disk, but a hard disk usually won't fit into a device built for SSDs.

• More ruggedness. Solid state disk do not have moving parts and are inherently more immune to shock and vibration than rotating hard disks with the seek heads surfing on a thin cushion of air. Altitude isn't an issue, they're immune to magnetism, and SSDs can handle extreme temperatures better than hard disks. The latter often come with disk heaters, but that means extra expense and battery power.

Not all SSDs are the same

More sophisticated solid-state disk technologies cost more and provide much better performance. To the extent where picking the right SSD can have significantly more impact on overall performance than the CPU itself.

Unfortunately, leading-edge performance always comes at a cost. Just as there are Intel processors that cost more than an entire premium laptop, state-of-the-art high-performance SSD also cost extra. A fast high-capacity SSD module can easily cost as much as a premium tablet or more.

What does that mean? In essence that as long as cost is an issue, which it almost always is, it's good to keep an eye on emerging SSD technologies and pay close attention to bargains. Bargains can be found when a manufacturer seeks to popularize a new technology by making it available built to a price, perhaps by cutting a feature here or there, or by lowering prices on capacities and features that are no longer at the bleeding edge.

The PCIe standard, on the other hand, can reach theoretical throughputs of up to 4 gigabit per second, depending on which PCIe standard is used and how many lanes are available.

We got our first practical demonstration of that in Summer of 2017 when Xplore Technologies managed to get a stunning performance increase in the top-of-the-line configuration of their XSLATE R12 rugged tablet. A prior Xplore XSLATE R12 we had tested in October 2016 came with an Intel Core i7-7500U and a 256GB SanDisk SATA 3 SSD. The Summer 2017 machine Xplore sent us had a Core i7-7600U and a 1TB Intel 600p Series PCIe SSD.

So what is the Intel SSD 600p Series? It's a small memory module. It comes in the M.2 22 x 80 mm form factor and uses a PCIe NVMe 3.0 x4 interface.

M.2 is a specification for internal expansion modules that use the PCI Express Mini Card physical card layout and can be built with a PCI Express 3.0 (up to four lanes), Serial ATA 3.0, or USB 3.0 interface. The 22 x 80 refers to the module size in mm. NVMe (NonVolatileMemory) is a protocol that speeds up data transfer between module and computer on a PCIe bus. And PCIe 3.0 x4 means version 3.0 of the PCIe standard, using four lanes.

According to Xplore, the XSLATE R12 has a 2-lane PCIe implementation, which literature suggests would result in a maximum real-world throughput of roughly 1.6GB/s. The Tom's Hardware site examined the Intel 600p 1TB NVMe SSD in detail (see here) and considered it an "entry level" competitor in the NVMe 1TB class, but appealing due to its attractive price (about $350).

Truth be told, between different technologies, interfaces, architectures, implementations, drivers, firmware and optimizations, it gets pretty involved very quickly. So off the cuff, we looked at the roughly 600 megabit per second max throughput of the SATA-based SSD in the last XSLATE R12 we tested, and then the estimated roughly 1.6 gigabit per second of the PCIe-based SSD in the latest test R12 Xplore sent us, and we figured there might be as much as a 2.5X increase in disk performance.