An MBA is traditionally a 2-year degree and has nothing in common with the MD curriculum so it would seem that an MD/MBA would take six years. However, all the programs I see are five years. Is part of the MBA curriculum missing for these combined programs and are graduates of 2-year MBA programs stronger than their 1-year counterparts?
It depends on the program, but most institutions mesh them together in some fashion...
Summer classes during MS1.
Cut clinical elective time during MS4, replaced with B-school curriculum.
Slightly shortened business curriculum to earn the MBA.
...all ways that 4 years of med school and 2 years of b-school is squeezed into the 5-year MD/MBA.
Now, does that make for "weaker" graduates? I guess it depends.
Intellectually, I imagine the MD/MBA students at a specific school are as strong as any of their pure MBA counterparts.
In regards to knowledge, it is a trade off. You might have less knowledge about some intricate financial instrument (since perhaps you never had the opportunity to take the elective covering said matter). However, you bring a different pot o' knowledge to the table that your pure MBA counterparts don't have: your clinical knowledge.
In regards to networking, the 2-year pure MBA has the upper hand, given that as a MD/MBA student you likely will not have the same freedom/breadth of networking, option to engage in a lengthy internship, etc. However, if you aren't looking to work for GS as a MD/MBA graduate, this fact might not matter as much.