Roger,

The important specs is dependent on the application.

For example, if you drive the MosFet from a logic level chip, say a MCU, then you want the Vgs to be as low as possible for the MosFet to be fully closed and have minimum Rdson

Other spec like the circuit on the above Note, is the Rds itself, so you don't have thermal losses.

Also the Vds max should be more than the worst case on your circuit voltage levels.

Ioannis