What they're made of
James Hardie is fiber cement — cement, sand and cellulose fibre pressed into boards. It's heavy, it doesn't burn, and it doesn't rot. LP SmartSide is engineered wood — wood strands bonded with resin and wax, with a treated overlay on the face. It's lighter, cuts like lumber, and comes pre-finished from the factory.
How they look
Up close, SmartSide has a deeper, more convincing cedar grain. Hardie's texture is a little flatter and more uniform. From the street, most people can't tell them apart. Both come in lap, panel, and board-and-batten, and both have a factory colour line (ColorPlus for Hardie, ExpertFinish for LP).
Cost
In our area, installed, SmartSide usually comes in 20–30% under Hardie for the same profile. On a typical 2,000 sq ft house that's roughly $30,000–$50,000 for SmartSide versus $40,000–$70,000 for Hardie. The gap is mostly labour: Hardie boards are heavy, they need a dust-controlled saw, and every cut is slower.
How they handle winter
Both handle freeze-thaw well, which is the thing that kills cheap siding around Georgian Bay. SmartSide is more forgiving in cold weather and takes a hit better — a hockey puck or a ladder bump dents Hardie but usually bounces off SmartSide. Hardie wins on fire and on the fact that it's completely inert; it won't swell if a cut end is left unsealed. SmartSide needs every cut end sealed, which is an installation-quality thing, not a product problem.
Warranty
Hardie: 30-year non-prorated on the board, 15 on the ColorPlus finish. LP: 50-year on the substrate, 15 on the ExpertFinish paint. Both are better than you'll ever need if the install is done right.
Our honest take
If you're staying in the house 10+ years, want the name buyers recognize, or have a fire concern (rural property, wood stove, close neighbours), go Hardie. If you want the wood look, you're watching budget, or you're siding a cottage that takes some abuse, go SmartSide. If a contractor only pushes one of them, ask why — it's usually because that's the only one they're comfortable installing.
We'll bring samples of both and hold them up against your house in daylight. That settles it faster than any article.