I bought the 720 watt version which uses Samsung LM301h vs the 900 watt with LM281b. I was talking with the support team from the manufacturer after I placed my order for the 900 watt version and he explained the difference since they have two 720 watt variants but only one 900 watt version.
So I paid $500 for the 900 watt version then he assisted me in switching to the more efficient newer LEDs instead in a 720 watt version with the newer diodes.
So the newer lights are more luminous per watt, while consuming less wattage vs the 281b diodes. Having two extra light bars will definitely compensate for sightly less efficiency.
lm301h are 0.2 w with 220 lm/w
lm281b are 0.5 w with 165 lm/w.
Regardless though both great lights in my opinion but I'm sure the newer version will also run slightly cooler as well with the newer diodes and less light bars.
Thanks everyone for the replied, happy growing growmies.