Typically panels run 18-19v. So 200 watts of panel would be transferring 11 amps or so 200w/18v.
If the run is only 8 feet your voltage drop with 12 AWG is only about 1.5% That's fine, and that's at the panels full rated wattage which is something that rarely exists. Typically it is recommended to be below 3% voltage drop.
Going to 10AWG would give a voltage drop of about 1/2% less than the 12AWG. It is an advantage but a pretty small one. Is there a chance of adding more panels in the future? That would be a good reason to upsize the wires at this point in time.
