In general, monocrystaline is more efficient, and longer lasting than amorphous.
The cheaper ones are often amorphous.
Amorphous may be slightly better under a partially cloudy sky.
Efficiency is sort of irrelevant. What does it cost, per delivered watt? The exception being a small roof that needs panels that are high watt per square foot.
The big companies that have been at it for a while are
less likely to go out of business and stiff you on a warranty.
Wholesale solar is often very illuminating on the good deals to be had on panels.
Solar Panels from Wholesale Solar
If I could get amorphous panels for half the cost of mono-crystaline, I'd just put up twice as much, assuming both from a name brand company with similar warranties.
Ten years from now, I think it will look uneconomic to make electricity out of coal, with the possible exception of base load at night.
There's talk of .36 a watt solar panels on the horizon. If that happens, it's going to be a disruptive game changer. Hey, we can all hope.
I'd hate to see the big fossil energy companies suffer. I knew there was a fundamental sea change when traditional energy companies started buying pv manufacturers.