Two completely different creatures. Apples and oranges actually. The P5 is an analog monster with 2 osc per each of its 5 voices and had square, pulse, tri, saw wave forms. Sound wise, its hands down the quintessential 80's analog synth
The VS was a vector synth (digital) with 128 digital waveforms (32 user + 96 ROM) with 8 voices was 2 part multitimberal. It's sounds are much more digital sounding but it's evolving sounds are very unique (think movie scores). The VS evolved into the Korg Wavestation after SCI went out of business and Dave Smith was hired as the lead for Korgs R&D department in Ca. If your looking for VS type sounds, a Wavestation is a good alternative and even has most of the VS waveforms