Hearing is so subjective that it's impossible to be sure, but: I do prefer the sound of my spiderless repro from my 2-65 over any of my 'spidery' pot-metal (and brass) reproducers. I could be imagining it, but I think I hear less distortion and blast, especially on very late Orthophonic and early Victor Hi-Fi (up to 1935) records. The spider seems to introduce conflicting vibrations (possibly due to extra weight, mass, or a spring effect as Welch or somebody pointed out) to the diaphragm (if I were a Scientific Guy &/or knew what I was talking about, that is .... )
The portable reproducers also lack what I have seen referred to as a phasing plug inside the reproducer itself: a bullet shaped object cast into the back plate. Any ideas on its purpose? I agree that the later portable ones blast newer recordings less, though the surface noise of the disc seems to be amplified a bit.