"Analog" VSTi's and VA (Virtual Analog) hardware synths sound pretty much the same.
This is because they're both doing the same thing: simulating analog circuits with digital technology.
Genuine Analog hardware synths have a character (read: unpredictability) which VSTi's will never be able to recreate completely, but they're getting closer and closer to the extent that it doesn't really matter.
For my money, I'd say get a good controller keyboard and a couple of VSTi's.