I had thought that one would be executed much faster than with state execution, but that may not be the case. From 2009; not sure if it has been changed:
"Under the Uniform Code of Military Justice, the president must sign the order for an inmate to be executed.
In July 2008, President George W. Bush signed the order to execute Gray, 43, a former Army specialist convicted of multiple rapes and murders, but a federal judge stayed the execution and Gray remains on death row.
Gray has been on death row at Fort Leavenworth since 1988 when a court martial convicted him of murdering two women and raping three in December 1986 and January 1987 in Fayetteville, N.C."
abcnews.go.com/WN/militarys-death-row/story?id=9075282