This is true, but not by much
PhD: 42 y/o
MD: 44 y/o
MD-PhD: 43 y/o
per
The Vanishing Physician-Scientist? So whatever training path you take, on average, you will get an R01 around the same time. Absolute number wise, PhDs get more R01 grants, but proportionally to the number of a particular group holding a degree(s), MD-PhDs are the most successful group.
Either way you go into science will take almost a decade and a half to get a "guaranteed" job (more likely longer).
MD: Medical school (4) + Residency (3-5) + Fellowship (2-3) + Post-doc (2-3) = ~13
MD-PhD: MD-PhD (8) + Residency (3-5) + Fellowship (2-3) + Post-doc (2-3) = ~17
A quick note: If someone was to do a research residency like the ABIM Research Track then the training would go down for both MD and MD-PhD, although MD-PhD would likely have more training in basic/translational science and be more competitive. For this track residency and fellowship are combined into 6-8 years, with 2-3 years dedicated research time, so it is almost like an integrated post-doc within the fellowship. MD ~11 years & MD-PhD ~ 15 years. There are other research pathways such as Holman Pathway (rad onc & radiology).
PhD: Grad school (5)+Post-doc1(2-3) +? Post-doc2(2-3): ~10.
On top of any one of these paths, if you do manage to land an academic job as an assistant professor, you will typically hold this for ~5 years before you are up for a "guaranteed" job (tenured associate professor), and that is
definitely not guaranteed.