I doubt there will ever be unbiased information regarding wheel sets unless someone has devised a blind testing method.

Expectation bias is also a factor.

That said, this is my experience. (mostly subjective conjecture)

My first real bikes were mountain bikes, 26" wheels that proved to be quite durable, and the tire had the most influence on ride characteristics.

My current setup uses 700c wheels with 28mm tires.

The stock wheels I started with were absolute rubbish. Machine built, with low quality cup-cone bearings, mystery metal spokes, and heavy v section 28 hole rims.

The back wheel started breaking spokes, after a few hundred KM. In an effort to try to salvage it, I replaced all of the drive side spokes with high quality stainless spokes, this solved the spoke breakage issue, and lasted about 6000KM until the drive side hub flange cracked, along with multiple hairline stress fractures around rim.

I now ride on my own hand built wheels, using Sheldon brown's instructions. DT spokes, Alex ACE-19 32 hole rims, and novatec hubs. The difference was night and day, the old wheels rode very harshly, yet still had noticeable lateral flex. The hand built wheels are amazingly smooth. On decent pavement I find myself questioning the tire pressure.

I'm not sure if there was much of a weight difference, the new wheels seem to launch a bit better off the line, but with this is probably subjective. More confidence probably means more power applied to the wheel.

My next project will have 26" wheels, I tend to punish my wheels more then most riders I know. I miss bombing down stairs, and jumping curbs etc.