Hardwood vs engineered wood

Most Eichlers were built without a vapor barrier beneath their slabs. One way to mitigate moisture coming through to your wood floors is to first lay down 30# roofing felts (lapped 12") before applying any subfloor (such as 1/2" exterior grade plywood). If you do put down a plywood subfloor, roll out a sound underlayment prior to laying down the floor planks....
Hardwood is not as durable as Engineered but you can always sand hardwood down to apply a new finish...(though some engineered floors can be refinished)

In a couple of our bedrooms I put in a floating engineered wood floor. I used an underlay for padding and moisture barrier. I liked the engineered wood planks (used Bruce brand). It's definitely better than the Pergo-style flooring. The planks have more wood-like characteristics.

I thought the floating method would be the fastest (since I had limited time for the installation). In hindsight, I think I would prefer sealing the concrete with a painted coating, and then gluing the planks down. I don't think the "padding" provides that much benefit. The downside is that the padding sticks up in some places where it has expanded.

With engineered planks, the top layer is relatively thin. They claim its good for 3 refinish jobs. But I would say one maybe two. So if you expect to use your floor very long-term, solid hardwood planks may be a better fit for you.

Good luck.

A follow up note to my previous message.

One un-sung benefit of a floating installation is that if you mess-up (which I did a couple of times) it is super easy to take apart and re-install. If you're going to do it yourself and you don't have that much experience with floors, that might be something to consider.

Tip for re-installing: mark on the back of the planks some numbering, and figure out some systematic way of bundling the planks together as you set them aside.