Is anybody know if Fiber Cement has some downside? thanks

Not as easy to work with. Dust from cutting is extremely dangerous and ofter overlooked by contractors working with it. Requires painting. More expensive than vinyl. Requires a more skilled installer.

Dust is the big one really.

Thanks

Planks break easily if not handled carefully. As for the dust problem I bought a pair of FC shears. IMO, they worked quite well, allow you to cut gentle curves, and don't create any dust. Easier to use than a circular saw, I don't know since I never used a circular saw to cut Hardi, but considering the dust aspect I would be inclined to say they are. To cut holes for electrical boxes, etc., I used a masonry bit to drill starter holes, and then did the cutting with a jig saw carbide edge tile blade.

If you buy primed planks, not factory painted, I would suggest you prepaint the first coat before putting up the siding. Two benefits, first you get paint over the entire surface including both edges, and second, you don't need to be concerned about getting them painted within Hardi's 180 days after installation requirement to preserve the warranty.

Read NER 405 for complete report on Hardi products. Respirators and common sense help on an install. Wind load is critical for attachment [especially in Coastal Zones]. Biggest Problem is sealing and caulking. Any cuts and joints have to be protected from water intrusion or you'll watch it fall apart before your very eyes.