The Premier and the Beechjet, while they share some similar systems, are really totally different animals. The construction and dimensions are different.
The Premier has a max gross of 12,500 lbs as opposed to 16,300 for the Beechjet, and is certified in the normal category, not the transport category like the BE-400.
The Premier is a RA-390. You can have a RA-390 S rating which will allow you to fly single pilot.
Showing an employer jet experience will be required. The BE-400/MU-300 will be good for that.
I had no previous Premier experience (Came from CE-560, where most of my time was SIC).
There are just over 200 Premiers in the world, and less than 800 typed pilots. There are oodles and oodles of Beechjets.
Premier specs:
http://www.hawkerbeechcraft.com/beec...fications.aspx
Hawker 400XP (Beechjet) specs:
http://www.hawkerbeechcraft.com/hawk...fications.aspx