They are designed with quality components, and with the idea of being stable under load for longer times. They are meant for business use, and downtime impacts work and revenue.

Depending on the model, another feature is the option to have way more ram than on a consumer system.

Lastly, the warranty includes an onsite support with quicker response time, and good phone assistance in case of issues

Backing what mazzinia said, Precision's are faster with loads.

New technology goes into a Precision before something like an Optiplex (business class) and some other consumer or at home systems.