The DELL XPS 13 has an SSD storage medium which is better than most similar spec portable PCs that were launched more than two years ago. Most comparable spec notebook PCs that were released more than two years ago 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 actually the best storage medium across all medium processor core laptops that have been available for around the same time as the XPS 13.
An HDD storage medium is the worst storage medium across comparable types of notebook PC.
Other notebook PCs that have an SSD storage media currently available which you might want to consider include cheaper portable PCs such as the HP EliteBook 820.
Portable PCs with a better storage medium that might also be worth considering include the HP Pro (SSD), or the DELL XPS 13 (SSD).