Night vision and Thermal are very different technologies. You can think of night vision as a super-power that allows you to see, just like your natural eye, but in very dark conditions.
All night vision needs a little bit of ambient light to work, for example the moon or some starlight. Additionally, the SiOnyx night vision is full color and our Pro version will operate in "moonless starlight" conditions.
Thermal picks up on "heat signatures", not visible light. The benefits of thermal is that you don't need any ambient light and you can see in the pitch black as it's not looking for visible light, and only reading heat signatures.
Powerful enough thermal can also punch through fog, again because it's not looking for visible light, and only reading heat signatures. Unlike thermal, color night vision will allow you to identify what kind of animal is looking back at you in the darkness. Whereas thermal, will only pick up their heat signature.