No one can answer your question definitively because it comes down to your subjective impression.
I have used both casters and hard rubber hockey pucks alternatively in place of spikes. Imo, the activity of lofting the speaker via these devices is dependent primarily on the elevation and not nature/quality of the device. I used casters on the Vapor Audio Joule White speakers on carpet, and the elevation change was to my ears beneficial. I am not saying there could be no variance in sound quality with other lifting devices, but given you practical circumstances and the benefit of precise positioning, I suggest that with the dozens of ways to improve audio systems it would be sensible to use casters. Imo, the benefit historically of elevating the speakers has far outweighed the possible degradation of spike vs. caster. If there is a variance in elevation, then that alone would nullify any attempt to declare one better than the other, as they would both have to be the same height to make a proper assessment.
i.e. Focus on the major variables, and build your system practically so that you gain the obvious advantage. You are thin slicing your system, which is counter-productive to advancing it well. Put the casters on the speakers, then begin an assessment of entire sets of cables and you will move the rig much farther ahead than you dreamed.
To show you how much potential exists and how placing too much emphasis on such things as spikes/casters is counter-productive, have you ever considered that the absence of baffle slope is not advantageous to the best performance of such speakers? Try this; place a thin shim (i.e. about .25" coaster, or furniture leg puck) under the back of the speaker stands, and prepare to be wowed. Using such dipole speakers without forward baffle slope loses a LOT of the beauty of the technology. I always lift the back of any big speaker, as it changes dramatically - and I do mean dramatically - the entire character of the speaker. Try it, you'll see. You could obtain a somewhat similar outcome with the stands if you can place washers or similar between the speaker footers and the stand, and still use the casters.
I also presume you are using some degree of toe in. If not, then when you lift the back of the speakers, toe them in to hear the benefits I am discussing. The effect would not be as strong if they are parallel to the head wall.
You follow all this advice, and you will gain several important advancements to your system. :)
