Hi, I have googled about everything I can think of, but can't find an exact thought on this question: when choosing engineered hardwood to be glued down over concrete slab on ground level, what is more important to how the floors will wear:

3/4 inch engineered hardwood
the overall thickness of the engineered wood, OR the wear layer? Case in point:
choosing between Mannington oak which is 9/16" thick but only 1/12" wear layer OR Mirage oak which is only 6/16" thick but has a thicker 1/8" wear layer? Thanks for any and all advice!! (Both have 25-year finish warranties)

IMO, the general consensus is the wear layer is more important. Both of the products you mentioned are quality floors. However, the Mannington is a rotary cut veneer. I am unsure of the veneer of the Mirage but if it is a sawn veneer, that is considered preferable. I also believe that the thicker wear layer will withstand a greater PSI, similar to what the solid PSI number would be. For N. Red Oak, that is 1290 PSI. This means greater dent resistance. The thicker wear layer also will allow a complete refinish ( sanding ). Thin wear layers MAY be able to be resanded but the chances of sanding through the veneer are greater. All things considered, the thicker wear layer with a sawn veneer is a superior product in most situations, regardless of the overall thickness of the engineered flooring.

Wow! Thanks for the quick response. That's what I was assuming (the wear layer is most important), but I valued your other info as well. My hardwood guy is coming in the a.m. & I need to make a decision. THanks again!

I agree with Gary's comment about the rotary and solid sawn veneer but what is used for the next layers are just as important. If you use a 1/8 inch oak top layer and a softer wood for the next layers that 1290 psi would not mean as much as if you used oak all the way through. When I deal with my customers I recommend they look at more then the wear layer.

How would I be able to find out what the other layers of the 5-ply construction are made of? The sample indicates Red Oak, and it's 5-ply, with the 1/8" wear layer. I just assumed the entire thing would be red oak (I'm a "hardwood newbie"; never done this before). Thank you for your input. (By the way, has anyone had experience with Owens engineered hardwood? That's the other manufacturer I might go with and it has an even thicker wear layer -- 3/16" thick; but of course, it's even more expensive than Mirage & Mannington).

The janka ball test (psi) pretty much means nothing when it comes to engineered, thats only for solid hardwoods due to the cross layering, adhesives thickness of plys and other species used for the underlying plies.
I tell my clients to look for a moderate thickness wear layer and the finish being of upmost importance.

I am familiar with Owens unfinished oak, engineered. Very high quality. Sawn top layer, all layers oak, precise milling. Unfortunately not familiar with their finish.

The Mirage product is 1/8th inch wear layer of solid sliced wood so visually it will appear identical to a solid floor. Rotary peeled veneers will look similar to plywood.
Also, the sub-structure of the Mirage product is made up of 6 layers of baltic birch which has proven to be one of the most stable woods available to us. This is the case for the glue-down or nail down Mirage product.
Their float floor is a thinner surface (still sawn face) attached to HDF core and a thinner bottom layer of wood. THis is also a very stable product but I have never been a fan of MDF or HDF cores, although they seem to have proven themselves in the field.
Taber testing really doesnt have much value to field longevity, unless you are in the habit of walking on your floors with your golf shoes on.
More important is the quality of the finish, which you really will have to rely on your installers knowledge and integrity, since all flooring manufacturers claim to have the best. I have yet to encounter a flooring manufacturer who was willing to say : Our product is almost as good as the others"