Longer lifetime if you're writing a lot?
In a laptop? I seriously have my doubts that the advertised MTBF will be valid if the drive is not mounted in a shock free, climate controlled environment.
15K RPM drives are so sensitive to vibration and shock that they can't even stand
being shouted at
, let alone being tossed all over the place. They also don't have G sensors that will park heads in the event of imminent shock like almost all current 2.5" SATA disks do. If you do an insane amount of writing, you can put a RAID1 SSD setup in them and just replace the drives that fail before you lose data. You can get over 500G SSDs for prices comparable to the same storage in 15K RPM now and you'd still be faster with the SSD in latency, transfer rate and IOPS. Just keep replacement drives on stock and you shouldn't have a problem with availability of your system.
15K RPM disks run much hotter than slower disks. This means they require much more air flow, which you will also have to provide. Sure, they'll run at the higher temperature, but the constant temperature changes will make the bearings wear much quicker and the magnetic density and track width will vary a lot more than in a temperature controlled environment.
The laptop I'm typing this from has "Mobile Workstation" on it. It's now 5 years old and apart from replacing the keyboard 3 times due to worn keys, It's basically still the same as when I bought it. Yes, I've upgraded it from a single 160G drive and a DVD burner to a 160G+500G and I've gone from 2G ram to the max of 4G. Other than that, it's still the same and I will probably replace the 160G drive with an Intel 330 240G SSD in the coming months. It would be able to run Windows8 just fine if it would have the EFI stuff MicroSoft requires. It would be able to run the latest OSX version just fine if Apple would allow it as well. The current offering from the vendor that is the "direct replacement" will come with 16G ram, a 1920*1050 IPS panel, a quadro GFX card and a 3rd gen intel quad core I5. Mine is a 15.4", but you can get a 17" version as well. Mine will do two external monitors using HDMI and VGA, or on a docking station you can use dual link DVI to drive a 2560*1500 or so monitor in combination with the laptop screen. The successor will drive dual display port screens at that resolution plus the laptop's own panel.
There are at least two comparable offerings in specs from major other vendors, so there is a market and there is competition in it. These are high spec portable computers that are using dedicated hardware designed for portable use. Look at what a portable workstation will be used for, what environmental conditions it will encounter and then pick the hardware that is most suitable for that. If you start putting a desktop computer or a server into a smaller enclosure, you don't get the best portable computer, because the components in it aren't designed for that and the philosophy of their design doesn't fit with portability.