The future of storage in ultra-thin portable devices such as Ultrabooks is clearly SSDs, but the major storage companies haven’t given up on traditional hard drives just yet. Back in April, Western Digital shipped a 5mm thick 500GB hard drive, and now Seagate is doing the same to offer up some healthy competition in the form of the Laptop Ultrathin hard drive.There doesn’t seem to be much differentiating the UltraSlim Western Digital and new Seagate drives. They are both the same size, offer the same amount of storage, and prices start at $89. That makes them significantly cheaper than an SSD, albeit slower and more power hungry. But even with that being the case, both Asus and Dell have apparently already placed orders for the new drives for use in laptops and tablets.One area of the drives where Seagate and Western Digital do differ, however, is in the connectors used. WD opted for a new integrated connector that combines power and data transmission. Seagate on the other hand is sticking with the more traditional SATA connection and separate power connector. That should make it easier to use the drive with existing hardware designs, albeit at the cost of an extra cable.The space and cost saving a 5mm hard drive offers should enable lower-end laptops and budget Ultrabooks to get a little thinner. Alternatively, battery capacity could be increased, and hopefully that’s the route taken by most vendors. I think for the most part laptops and Ultrabooks are thin enough, we just want to be able to use them for longer away from a power outlet.