Anyone telling you otherwise about either one has outrun the literature
Experimental Interaction and Research Focus Interaction with intracellular signalling networks in controlled laboratory models Influence on transcriptional behaviour and gene expression pathways Modulation of enzymatic sensitivity and biochemical response mechanisms Impact on mitochondrial activity and cellular energy regulation Support of repeat-exposure and comparative pathway validation studies Laboratory Research Applications Cellular Repair and Regeneration Research: Examining cellular response behaviour and regenerative pathway modelling in vitro
Specifically, it is found in blood plasma, saliva and urine
Also, a central clock, independent of the SCN, can be entrained by food availability, temperature variations, forced activity and rest, drugs (melatonin itself), and timing (50)
One more note: because DSIP is still under investigation (and regulatory status varies), both delivery routes are best viewed as experimental or investigational not as guaranteed therapies