The cbp.gov website doesn't have clear instructions on who is considered a resident vs visitor for customs purposes.
There is limited information online regarding the same. Can somebody please clarify?
Similar to Doc, while living in the USA and having an H1B visa I have always chosen the 'Resident' option when entering the country.
After all, I am a resident for tax purposes and I am not required to maintain a residential address in my country of origin while living & working in the USA.
With regard to your other question posted as a comment to Doc's answer - no the primary purpose of your visit is not business.
When you're on an H1B and employed by a USA company, you're not 'conducting business' in the USA any more than Mr Joe Bloggs American is conducting business when he goes to work.
If you were a foreign business person entering on a B visa in order to visit an American company who is a customer of yours (for example) then this would be 'conducting business' and in this case you would choose 'yes' for that question.
Personally I have always answered "Resident", and on the one or two occasions that I've asked the immigration staff about this they confirmed that this was the correct answer.
(I'm not on a H-1B, but a visa that is functionally equivalent as far as this question goes)
Technically whilst in the US on a H-1B you are a "Temporary Resident", as distinct from (for example) a Green Card holder which would be a "Permanent Resident".