Instruction 3 on the Instructions form for I-751 says to submit "Financial records showing joint ownership of assets and joint responsibility for liabilities, such as joint savings and checking accounts with transaction history..."
Why would it make a difference if he uses one account more than another. Submit them all. If you do not, you are not following the instructions and basically asking them to reject your application for noncompliance.
See the instructions link below
This does not constitute legal advice or the engagement of my services as an attorney.