Do speakers sound better on wood floor or concrete

Interesting question, but....nobody wins the bet, too many variables. Wood may resonate more than concrete, but at what frequency? Most concrete floors are covered in carpet which dampens the first order reflection from the floor. Bass travels through and resonates most solid surfaces, regardless of the material. In my view, the best surface is a hand-laid hardwood floor on a solid subfloor using the came wood as the floorstanding speaker cabinet, with an authentic hand-made Persian rug to soften the first reflections!

The floor should not be part of the sound at all - at least not directly from the speakers' bodies! That's why you use spikes, antispikes and the like!

The great concert halls have wood floors, so I'm guessing that's the absolute best you can do, if everything is just right, wood wins. That of course is just for arguments sake, as a real world practical issue it depends on many construction variables.

A lot of it has to do with the structre of the floor. Is is a wobbly suspended wooden floor with a basement like I have? I had to cut away the carpeting, screw down 3/4" plywood and then install floorjacks right under the speakers from the basement. It worked wonders! Also kept floor vibrations away from the rest of my system especially my turntable. In fact in did the same thing to my TT. My basement doesn't look real nice, but no buddy goes down there anyway. And good spikes are a must.
Good Luck!
Chris