A helical spring is not a sinuous spring, but a coil style spring. These can be implemented in several different ways so its hard to tell by the description what the exact construction may be. Hardwood laminate is another name for plywood. Overall, this seems to be a fairly typical mid level construction and looking at the prices on the Arhaus site, they are a bit high for the quality. Before settling on this, get out of the chain stores and get into some local independent dealers. You tend to get a wider selection of brands and don't have the mystery of who is actually making the furniture for the chain stores own branding.

The Leeward style made by Arhaus has a plywood frame and what sounds to me like a drop in coil spring unit. This is a coil unit made outside the furniture, not built in and then screwed into place. It can be 8 way tied or not. A true 8 way tied is better as it is built into the frame and and adds to the torsional strength of the sofa. Many of their sofas are made by a company in North Carolina called Thomas Bain of Conover, NC which makes a pretty nice product.

The Crate and Barrel Lounge sofa has what is called a Flexolator spring and a plywood frame which is essentially a rectangular wire grid attached to the frame with little wire springs. I think this sofa is made by McCreary Modern of Newton, NC.

The Z Gallerie sofa has what I think is a plywood frame with Sinuous Springs and I am not sure who makes this.

A solid 5/4 hardwood frame is better as far as the spring construction I suggest you research various springs constructions your self including true 8 way hand tied and then draw your own conclusions.

I would think the cushions, and tailoring on all are pretty good.

Both Sir John and Freethinker99 have given excellent analyses on the various options available.

On the other hand consumers must constantly balance questions of quality vs. cost.

There is no doubt that 8 way hand tied coils and 5/4" solid wood frames are superior to drop-in coils (or no-sag) springs and plywood frames.

On the other hand a well-built plywood frame sofa with an inexpensive no-sag spring system, costing many hundreds of dollars less, can still be expected to last at least 10 years.

Cushions and fabric are far more likely to wear out long before the frame and springs.

On sofas retailing for under $1500 by far the most popular type of cushion construction is a 1.8 density HR (High Resilience) polyurethane foam with a polyester fiber wrapping.

This type of cushion construction will typically hold up for only 3-5 years before beginning to lose its shape and resilience.

If you are looking for a sofa to hold up for 10 years you will need to upgrade your cushions. The two most popular upgrade options include spring-down or high density foam cushions.

Spring-down cushions are constructed using a coil spring system inside which is surrounded by foam and typically topped with a down/feather/fiber blend.

Another popular cushion upgrade option is one using a high density foam. The higher the cushion density, the more foam is used per cubic inch and the greater the cushion durability.

Although a 2.0 density HR (High Resilience) foam is a definite improvement over the standard 1.8 density, I would recommend a 2.2 density or higher if you want your cushions to last 10 years.

Fabric durability is the other primary concern for a sofa lasting 10 years.

Although there are literally hundreds of variations that can affect a specific fabric's durability, in general look for thicker, heavier fabrics that are tightly woven.

Keep in mind that a fabric's cleanability may also be a factor as a "dirty" or badly stained couch is unappetizing no matter how long you have owned it.

Liv did you pick one of these sets?