The Lenovo X1 has an SSD storage medium which is better than most notebook PCs of a similar age and type to it. Most medium processor core laptops that were launched around the same time as it have an HDD storage medium. Solid State Drives (SSD) store data in semiconductors on a circuit board rather than using magnetic or optical media. Solid State Drives have no moving parts which makes them very fast and reliable.
An SSD storage medium is in fact the best storage medium amongst all medium processor core laptops that have been available for around the same time as the X1.
An HDD storage medium is the worst storage medium across comparable types of portable PC.
There are a number of alternative portable PCs that have an SSD storage media currently available that you might also want to consider including cheaper notebook PCs such as the T420s, or the T420s both from Lenovo or the DELL XPS 13 ($719.00).
Portable PCs with a better storage medium that might also be worth looking at include the HP Elitebook 820 (SSD).