I should also point out that a DAR applicant must give more proof of descendancy than the SAR applicant. I applied to SAR and where there were holes the SAR genealogist worked to get it approved. It's legitimate, but SAR will take anyone who has even the slightest connection to the Revolution. Even if all they did was provide shelter to a soldier, it counts with SAR. DAR is a little more stringent along those lines.
But I do believe SAR has some very good genealogists working for them, and I would trust anything they find.