Definitely get 24V or higher panels. 12V panels won't recharge your batteries as fast and don't really cost much less (if any) per watt.
I just installed a solar system on our 2011 Winnebago View 24K using one 250W / 30V / 8.32A / 15% efficient Renogy Solar monocrystalline panel, 40A Renogy MPPT charge controller and MeTer LCD charge controller display a couple of months ago. Best price per watt by far and the largest single panel we could install with our limited roof space. The 250W panel was only $238 vs. my second choice of the significantly higher 20% efficient SunPower E series panels... but they cost $495... If you can find them.
My charge controller Meter showed this panel outputting 34.7V and providing 13.1V / 11.0A on a recent SoCal clear June day from the charge controller to our two Sam's Club Energizer (Johnson Controls "Varta") GC2 Premium 232Ah 6V batteries in series. REALLY pleased with the system, especially since the total cost including all the wires, fuse box, fuses, conduit, connectors, mounts, etc. was under $700.
