It has about 1m more of lifting power.....of course if you throw in another D5 so you have two in series you will effectively double the lifting power...so at a zero flow rate it would be rated at over 7 meters (7.4 theoretical but like SLI and crossfire setups, dual pumps will not scale 100% lol ).
Thats what I'm doing with my dual pump setup since i will have an external box underneath my desk with the puter on top, and I want a good flow rate and some headroom for additional blocks like another GPU or something in the future.