Why the incentive exists
Builders often offer closing cost credits for using an affiliated lender. The incentive is real and can be worth thousands. It is also a marketing cost the builder has already priced into the business.
The credit is not automatically the better deal. Compare the total: rate, points, lender fees, and the credit together, over the years you expect to hold the loan.
How to compare fairly
Ask both lenders for a loan estimate on the same day, for the same loan amount, with the same lock period. Rates move daily, so a quote from last week is not a comparison.
Then look past page one. Compare the origination charges, the discount points, and the cash to close line. A lower rate with two points is not always the winner.
What you should not trade away
Responsiveness matters on a build. Ask who you will actually talk to when a draw is delayed or an appraisal comes in low. On a twelve month project, that answer is worth as much as an eighth of a point.