Hi Shannon
I've been working with card and paper for over 30 years and I don't believe there is a simple answer to this apparently simple question.
Much depends on what you want to do with it, what stock you can purchase easily and ecconomically wherever you live and much more.
Ask yourself instead:
What product do I want to make 24/7: (there is no "right" way)
A reliable clone for the next 5 years or an artistic creative changing every few months.
Use new stock or what you already have. Be known for re/up cycle or new.
Check, research, analyse:
What sells: trawl shops which are selling masses: go figure the trends.
Does size/weight matter in other ways - eg shipping costs, creasing, cutting, printing, painting, embossing, etc.
Things like smoothness/texture/gloss or matching envelopes may be important to your style or market target.
230gsm in one card may feel very different in another from a different manufacturer.
Look at your product as a customer: what cards weight/style would you expect/like or could you care less, it's the look/colour etc which matters.
Research, research.
Even after all that, be aware that you may need to adapt quickly or over time.
Alternatively, if you are an experienced maker/seller and believe in your product, whatever it's made of: launch as an act of faith in your product and be prepared to adapt.
I'm sorry I can't give you a definitive answer, if it was easy we'd all be millionaires!
