Definately look at price per watt.
Still there may be some variability. I am still trying to figure out the calculations.
For example, if you are feeding a 12V battery,
Shoot for VOC (Voltage Open Circuit) of around 18-20V for a 12V panel.
Short circuit Amps may or may not represent the number of amps you can push into your batteries.
Note, as you approach the VOC, the power (amps) drops significantly.
Thus, say you have a 12V panel, VOC=20V, With Short Circuit=2 Amps
I presume your Maximum Theoretical Watts is somewhere close to 2 Amps * 12V = 24 Watts (not 40 Watts using VOC in the calcs).
However,
If you are buying bare Cells... they may be rated on the VOC and Short Circuit AMPS.... So, it may seem as if you have nearly double the power which really isn't there.
I believe that most 12V panels have multiples of 36 individual cells.