Answers

LP is a woodbased product, where Hardi Plank is a fiber cement. They ar both very similar in cost here in the midwest. LP Smartsiding if fairly new the market as well. 

We would suggest getting a ground mount system, not only does this allow you to place your array in a prime location but it will also save you the hassle of removing them down the road when the roof needs replaced.  Any solar provider should be able to show you the difference in production with a roof vs ground array. Good luck.