The Merlin has considerably higher specific impulse and thrust/weight ratios. It also has very fast throttling, a necessity for vertical landing. And, it's remarkably cheap (less than $1M per engine). I don't have the figure for the inflation-adjusted cost of the H-1, but I suspect it was much more expensive.
H-1: https://en.wikpedia.org/wiki/Rocketdyne_H-1
Merlin: https://en.wikipedia.org/wiki/SpaceX_Merlin
The Merlin has considerably higher specific impulse and thrust/weight ratios. It also has very fast throttling, a necessity for vertical landing. And, it's remarkably cheap (less than $1M per engine). I don't have the figure for the inflation-adjusted cost of the H-1, but I suspect it was much more expensive.