Go with the straight, hi res save from Photoshop for the best quality.  Yes, it is compressed but hi res will still generate a large file.  But not higher than PSD & PNG.  And from what I understand, merely opening and closing JPEG's in Photoshop will not degrade the image as Prof_Null stated.  If you manipulate the image, increase or decrease resolution for example, then the image will suffer degradation.  You can safeguard this from happening by creating a smart layer for your image before actual manipulation.