I too had this question. For my external mixer, I use a Keith McMillen K-mix which I love as it has bright lights and touch sensitive pads and provides 8 inputs/8 outputs plus on board reverb and compression effects. For modular mixers, I use my VCAs that have attenuators/inverters as well as a Doepfer A138c polarizer mixer and 3 channel Intellijel Mixup that has mutes and volume levels. The advantage of modular mixers from what I currently understand is the ability to mix CV and audio signals to create best submixes before send to a PA system or external mixer. Submixes are super useful! So if you have 4 voices and want to route these in creative ways then you can do so better than just send from VCA to an external audio mixer. I am saving for a larger case to get an all in one modular mixer that can let me route many voices and have CV control and mutes like the WMD Performance Mixer or the Befaco Hexmix.