A supersaw is just a densely detuned sawtooth. Even if you don't have the supersaw wave form in an oscillator, you can still emulate one.
One thing you haven't mentioned is voice count. The Poly Evolver has only four voices that can be played at once, the Prophet '08 has eight, and the REV2 has sixteen. The latter two instruments can do polyphonic layering, which the Poly Evolver cannot.
I'm somewhat generalizing, but any sound a Prophet '08 can make can be made on a Poly Evolver as well. The two instruments have a similar character, although the Prophet '08 does have a slightly warmer analog tone. But the reverse isn't true; that is, a Poly Evolver can do many things that a Prophet '08/REV2 cannot. However, it does have the disadvantage of a substantial amount of digital aliasing (noise) in the digital oscillators.