There's a few differences. The three main ones are capacity per square metre, predicted degradation curve, and weight. That all feeds in to the cost. Oh, and some of them have silver edges whereas others have black edges. So that might feed into your aesthetic. Generally speaking, a solar installer will offer you a choice - but it will be limited by whoever they have picked as a supplier. I'd recommend spending more to get a higher capacity. And if you have a weak roof, getting lighter panels is essential. But they're pretty much a commodity now.