Well... It depends. Think about your goals first, and don't worry about cost yet. There is plenty of free or low-cost software options out there that can teach

Well... It depends. Think about your goals first, and don't worry about cost yet. There is plenty of free or low-cost software options out there that can teach you the basics of either system. If you would like to just get your head wrapped around the basics of synthesis, it helps to limit what you have to deal with. With modular, to get a usable sound, you need to have at minimum: a gate/CV source (telling it when notes fire, and at what pitch), a VCO (voltage controlled oscillator), an VCA (voltage controlled amplifier), an envelope (to control the volume of the VCA), and an output (somewhere to send the signal - in this case, the audio-out of your computer. Then you have to deal with routing the CV signal to the VCO so it knows what pitch to produce, the gate signal to the envelope so it knows when to fire, the CV signal from the envelope to the VCA so it knows when to turn the volume up and down for each note, and audio signal routing. So it's a big bite to chew just to get started, BUT you learn a lot going this route, and there are a plenty of tutorials out there on modular that take you through it a step-at-a-time, most of which would apply to VCV Rack as well as to real modular equipment. If you start with the basics, tweaking knobs on a non-modular synth will be a piece of cake. But if you would just like to learn the basics of how the various components work together first, you can start with a simple subtractive software synthesizer, of which there are plenty of free options. Once you get your head wrapped around oscillators, filters, and modulation, you could then dive into modular to gain a more in-depth understanding of what is happening "under the covers." A lot also depends on what kind of music you would like to produce. If you are into generative music, where you are using devices to produce patterns in interesting and often unexpected ways, go modular, and don't look back. If instead your are mostly interested in driving a synthesizer with a keyboard, IMO, start with a basic subractive synth. Just keep in mind that no pre-packaged synth, no matter how flexible, can rival the sound-design possibilities of modular.