I get a kick out of mixing these, particularly on a school night.
These records are almost 30 years old. Prized possessions, both are original pressings.
In my opinion the Liquid Liquid is the superior track, the percussion in it outweighs the vocal in the GMF derivative. As far as I can determine, the "Let's Hear It for the B-Boys" remix isn't available on the 'net, so I've linked to the original below.
Left side: Liquid Liquid 'Cavern
' (Let's hear it for the B-boys remix.) Mo Wax
Right side: Grandmaster Flash 'White Lines
' (Original Long Version.) Sugar Hill Records