I've been searching the forums and trying to find out what scene scale I should be working at with Houdini. I have read in a some places that scene scale is 1 unit for 1 meter and also 1 unit is 10 centimeter. Which is correct? Or does it change depending on what your are doing?

It's a unitless unit except for Dops, which is set in Preferences. Hip File Options

That's useful thanks. I was confused by the enormous default toon rig.

Do most Houdini users default to 1 meter as standard?

I think cm is very popular but I personally like bigger scales!