My Gemeinde has said I can have a C permit when my B expires in March. I am a retired EU.
Can anyone tell me of any benefit to me to change.
Thanks in advance

You are a 'permanant' resident with a 'C' & must fill in an anuel tax return, after 5 years I doubt you have a choice, it's standard.

Depending on where you live you may get the right to vote on local or maybe even Cantonal issues / elections.