If you are trying to decide between hardware and software synth solutions, you should take a look at the Arturia’s new product. The Arturia Analog Factory Experience, based on the Analog Factory 2.0, combines both solutions (hardware + software) in an integrated system that can be used as a stand-alone program or as a plugin.
The Arturia Analog Factory Experience features a synth software that includes 3500 high-quality analog synth sounds (like minimoog V, Moog Modular V or Prophet V), a preset manager for quick finding them and built-in effects like filters, LFO, chorus or delay; and a hardware controller that features 32 keys with velocity sensitivity, 11 encoders (1 of them clickable), 4 sliders, 11 switches, 1 modulation wheel and 1 pitch bend wheel controls, hold, sustain and expression pedal inputs, USB port (the device is USB powered, although you can use a DC adapter) and MIDI connections.
This package works with Windows (2000, XP and Vista) and Mac OS X (version 10.3.9 or higher) and is available in VST, RTAS or AU plugin formats. The price of the Arturia Analog Factory Experience will be $349 but its availability has to be announced yet.