Harvest hasn't begun to use his full potential of his power. He's more of an arrogant villain than H'el. If you go by what Lobdell said about Harvest, than he's a Justice League level threat.
BTW, Harvest withstood the full blast of Anti-engergy by Wildfire and didn't feel a thing. Primarily from his force fields and was basically toying with the Titans.
H'el's able to rip something Kon apart molecules by molecules. He was literally studying him.
Supergirl was also tricked by his illusion, made Superman look like a chump, and he's shedule to take on the whole Justice League and Superboy in Superboy 16.
Strength wise he's as strong as Superman, just as fast and more dangerous.
Harvest as yet to show me anything that would put him on par with H'el. Harvest beat the Titans, so what. H'el did it even easier.