What matters most in solar is how many watts you have to run your loads. And how much it costs. PV modules, aka solar panels, come in all sizes and shapes and power outputs. Is bigger better?
You can arrange modules all sorts of ways. The basic rules are if you are putting them in series, use panels of the same amp capacity. If connecting in parallel, go with panels of the same voltage. Panels in use at my house range from 5w to 475w and 6v to 90v. They get along fine because I put blocks of compatible panels on their own charge controllers.
But what about those shiny new 500 watt panels you hear about? Why should I buy 190 watt modules when I can get 500 watts from one panel. Hold on now. A 500 watt panel is LOTS bigger than a 190 watt panel. About 3.5 feet wide and 7.5 feet long! It is also LOTS more expensive per watt. And HEAVIER! The only advantage in the bigger panels is the number of bolts you buy to hold those watts to the brackets.
For cost comparisons, Sun Electronics is selling used panels, mostly smaller sizes, for a dime a watt. For a while John had some 70 watt thin film panels that sold for 7 cents! The 500 watt panels are probably going to cost you 50 or 60 cents a watt. So, 500 watts for $300 or for $50? You decide.
There are other considerations, too. On a roof mount you might be able to place more watts. A recent boat forum had a post by a guy who wanted to max the solar on his boat, so he was going to buy huge panels. Well, I did that, too, for the Solar Yacht project. I bought a whole pallet of the 475 watt modules to replace the 330 watt modules I already had. The 475 panels should do well in some places, but the 330s and maybe even some 270s might be a better fit on the pointy end. That is yet to be determined.
The point is that space and money may be more important than having the biggest panels on the block.
Oh, by the way, John has 3000 190watt panels he needs to clear out of one of the warehouses before the rent goes up.
–Neal
