With Lion there are a bunch of unusual oscillators, like the Ringo and VOSIM modules, and a module that does a bunch of methods for combining them that aren't just a crossfade. The other synth that's like that (for the voice combiners) is DiscoDSP's Corona. With PhasePlant, you've got crossfade, AM and FM, although you do have a sampler module. So, there are things you can do in Lion that aren't, currently, possible in PhasePlant. The flip side to that is that the voice combiner modes are by their nature somewhat unpredictable in how they will alter the sound.
However, currently in PhasePlant's favour is that it handles MIDI CCs a lot better. I can't find a way to map CCs into Lion. OTOH, Lion directly supports MPE whereas PhasePlant doesn't.