This is entirely dependent on the soils and moisture.
In Dallas, most soils are expansive, with large change in moisture from season to season and during multi-year droughts. Not unlike seasonal freeze-thaw, we can get inches worth of movement in soil.
Floating and interior slab works fine if you plan for movement, such as under partitions. So a garage slab could float freely without too much trouble. Inside a house, you are inviting problems having a detached, floating SOG which is not protected from moisture-induced soil movement.
Sometimes the best course is a raft/mat foundation, but for houses, I find that piers supporting a perimeter wall and the interior of the house is the most stable and economical.
Also, is you have expansive clays, do not over-excavate unless your backfill is dense lean clay and is compacted. Do not use void forms under slabs where the base is below the surrounding grade for the same reason. I worked on a building with a slab over about 2 feet of loose, granular backfill. The fill acted as a reservoir for water, resulting in swelling of the underlying clays and raising the interior of the slab in excess of 6 inches over 40 years (just as ongoing plumbing leaks can do.)