I can't choose between them for some reasons.
(IMO) There are no essential or significant differences between them . They only have some (or more!) slightly differences. The Steven impact on P.T is very deep and complex even much more than Waters on P.F !
In my opinion , He used different sounding or different arrangement , mixes ,... in P.T and his solos to make some "Big and Clear Differences" to show to his fans and convince them :
" P.T and me are different and each of us have our own music."
(IMO) Steven is root and spirit of P.T and I can't imagine PT without Steven (can you?). In my Honest opinion P.T 's albums is Steven's solo albums too but with some slight differences !!! (with my honest respect to another P.T musicians)