To demystify all concerns once and for all, I work as a medical biller for a cardiologists' office serving both MD and DO physicians, all physicians get paid the same within their own specialty, unless they're enrolled in a special IPA program that buffs their pays by x-amount (let's say +25%).
If you do not believe me, just search up "CPT-4 fee schedule" (Current Procedural Terminology, Revision 4; fee schedule means how much they're going to get paid either as an in-network provider, or an out-of-network provider, servicing patient-X).
A standard office visit for all doctors in private practice can range from level I ($20~) to level V ($130~). You can find this fee schedule from Medicare's two websites (since all HMOs, PPOs, Medicare, and Medicaid plans follow Medicare's lead) on NGSMedicare.com, or CMS.gov, and just type in 2014 fee schedule. For services rendered, let's say you have a SPECT done, some people who are not enrolled in a special IPA will get paid ~$500, others who are enrolled in an IPA will get paid ~$600-650. But all in all, everyone gets paid the same, whether you're a new provider, or you've been grandfathered into a program.
Medicare as a guide for payments will always be your friend.
--Just my two cents.