Physician LOR hardly EVER "look better." Choose whomever has been around you for the more meaningful experiences. If both have just been shadowing, then I'd say look elsewhere for a LOR. If you have to choose between these two, go with the doc.
Did you work closely with this physician over a long period of time? Or was it just a shadowing experience? Unless you absolutely need a physician letter (some DO schools), using them is generally considered a bad idea. Shadowing a physician does not allow him or her to get to know you on a close enough level to write you a meaningful LOR. Such a letter would not help you one bit.