The Lenovo X250 has an SSD storage medium which is better than the HDD storage medium found on most portable PCs of a similar type and age to it. 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.
This portable PC's storage medium (SSD) is actually the best storage medium across all similar spec portable PCs that have been around for a comparable time to the X250.
The worst storage medium amongst similar types of portable PC is HDD.
It may also be worth also looking at one of the alternative laptops that have an SSD storage media currently available including a cheaper notebook PC such as the Toshiba Tecra Z40[plb_2355836_price], the DELL Latitude 14 E5450[plb_2794147_price], or the Lenovo L450[plb_2800034_price] or you might consider a higher rated notebook PC such as the Fujitsu Lifebook U745[plb_3000568_price].