How to tell the real difference between Panasonic panels?

I am shopping for Panasonic panels, and there are sooooo many models, and looking at specs they seem to be kind of the same? Other than obvious variation in wattage, but several models have same wattage.. whats the difference and how to figure out which is the best? Because they cost different amounts.

For instance the following ones: VBHN325SA16

vs

VBHN325KA03

vs

VBHN325SA17

or

VBHN320KA03 is more expensive than VBHN325SA16 with lower wattage. Why?

Thanks!