Soundstage, layering and tube differences

Within tube types, say el34’s, can anyone explain why one brand of tube like SED C’s have deep layered soundstaging and another, such as the Mullard reissue el34’s ,are more 2D? I just replaced my 10 year old SED’s with the Mullards ( which still need burn-in), but they are not nearly as 3D in my amps and are reported to be such.
Do some tubes resolve the actual recorded room acoustics better or is it a matter of harmonic distortion giving the illusion of soundstaging and 3 dimensionality??