I was looking at the 50 watt, and maybe 100 watt for one specific reason actually. I had read that you should only consider that about 70% of the wattage to make it's way to charging the battery. So, for 50 watt, that would only be around 35 watts that's useful.
The reasoning was that there would be some loss through the charge controller. Then, it's rarely going to be perfect conditions with direct sunlight and clear skies. Also, depending on the time of year, I could have some pretty short charging days.
I also want something to grow with. For now, I'd just be charging the Schumaker Power Station. It has it's on 18ah battery, and I have an additional 18ah battery wired in parallel with it for extra capacity. Later on, when we aren't saving for a new house, I am going to buy a couple of larger deep cycle batteries, a large inverter, and I would like to have a jump start of charging ability with the solar panel I have already purchased.
I'll probably go with the 50 watt for now, for space saving, and it is more portable.
I think, we completely hijacked the thread, got off point from the original power station question.