Mendocino,
The inside components (pump, heater, control box, motor (hp does change between units)) on all model numbers J-315 thru J-385 have the same exact components as the Sweetwater.
However, the top-side controls in the J-315 thru J-345 are different than the top-side controls in the J-355 thru J-385.
I would recommend you to look at the owners manual of the Sweetwater and Jacuzzi Premium. By doing so you will see the real similiarities between the Sweetwater and Jacuzzi Premium.
Chris H