Yes stratified society implies inequality. Spectrum is more inclusive, thus more accurate, but (a) it could be too complex for an analytical framework and (b) it doesn't imply verticality - it could be a horizontal spectrum unless specified otherwise. Hierarchy could be a better word to use since it implies verticality, and while it has less of an infinitely fractal implication than spectrum, it also has less of a finite implication than strata, so could still be the better word. Depends what exact vibe and meaning you're going for.