You are comparing your refund to the refund loan? That is apples and oranges. As for the refund itself---TurboTax and H & R Block (and all of the other software programs for do-it-yourself returns) have to comply with all of the current tax laws and undergo a stringent approval process by the IRS. So if you enter all of the same information into any of the software programs, your results should be the same. If your results are way different then it is because you entered something differently or incorrectly.
The refund loan program available from TurboTax is based on a number of factors including the amount of your refund.