The Latitude 6430u has an SSD storage media which is better than the HDD storage media found on most notebook PCs of a comparable 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 laptop's storage medium (SSD) is in fact the best storage medium amongst all medium processor cores notebook PCs that are a similar age to the Latitude 6430u.
The worst storage medium across similar types of laptop is HDD.