I can't comment to making the house look like it's worth less for tax purposes, but I can comment on Hardi siding and how much I like it. I'm a contractor and remodeler. If a client wants brick, I get the walls ready for it, then sub that work out. Brick is too tricky to do well unless you do it all the time. If the want real wood, I try real hard to talk them out of it and into Hardi. If they want Hardi, we're good to go.
It's easy to install, goes up quickly and is rather affordable. It comes primed and ready for paint. It holds paint really well and it's easy to paint. On the siding, I spray it, on the trim, I use a brush.
Comparing it to Certainteed, you'll find that Certainteed comes in pre finished colors and stains. I don't know the price of this but have seen a few buildings with it. Except for my being extremely critical of others workmanship, it's a fine looking product. The reason I don't use it is the only supplier is 100 miles away.
Smart siding is just OSB with a nice finish on it. It's easy to cut, nail and install. I've met builders who love it, but the few people that I know who have it, or know what it is, think it's kind of cheap looking. The fact that it's OSB makes me want to avoid it.
I'd be curious what negative comments you've heard about the Hardi siding?
Eddie