Slate discusses the pros and cons here: "Is It Better To See a Younger Doctor or an Older Doctor?"
In short, young doctors might be more familiar with the latest developments and technique. But older doctors might have more experience with unusual or tricky cases.
(The article is also careful to note that broad statistics might not apply to specific individual young or old physicians.)
The other twist is that young doctors appear to cost "the system" more, although the exact reasons aren't clear. It may be because they tend to order more tests to make up for their lack of clinical experience. Or perhaps some of them are seeing the sicker, more challenging patients.
(Note the Slate article suggests the opposite, namely that older doctors create higher costs.)
The policy implications aren't immediately clear to me, but I thought this might be interesting to those thinking of selecting a new physician.
In my Forbes piece from last month on protecting yourself from ObamaCare, I do note:
[I]f you’re approaching Medicare age (65) and your current doctor will retire in a few years, consider switching to a younger doctor now. Many doctors no longer accept new Medicare patients, and this problem will worsen with anticipated Medicare payment cuts. However, most doctors will continue seeing their current patients even after they turn 65. But if you wait until after age 65 to look for a new doctor, you may have a hard time finding one.