Hi,
I had a Vitamix (for 15 years), a coffee grinder for small amounts of flax seeds and a Thermomix.
The thermomix wins hands down! It is easier to use (especially as you can do any amount - either small or large), it is so much easier to clean so you don't hesitate to use it, it is less scary to use ( sometimes I thought the Vitamix sounded strained although nothing ever happened), and you don't need to change containers. Also stainless steel is much easier to clean.
I have now sold my Vitamix and never use the coffee grinder. The thermomix is truly a multi-purpose machine.