I have found spikes sound better. A compromise recommended to me by a dealer was to put the speakers/spikes on a piece of plexiglass...
Is Spiking Necesarry?
I like to move my speakers around a bit for to test how they sound, so I slide them. I have the Proac D48Rs, they are kind of heavy so with the spikes in it makes it tough to move them. I haven't consciously tested or compared the sound with spikes or without them. Does it make a difference?