What is the relevance of a !Q in the D Flip-Flop when using for a memory module?
Advantages of the first circuit over the second:


5 gates instead of 6.
two gate types (1- and 2-input NAND) instead of three.
gates that invert (NAND, NOR) are inherently simpler and faster than gates that don't (AND, OR).1
only 2 or 3 levels of gate delay between input and output instead of 3 or 4.


As you can see, there's no disadvantage associated with having the !Q output even if you don't use it.



In real SRAM chips, the transistors are made as small as possible in order to pack as many as possible into a given area. In order to maximize the reliability (internal signal to noise ratio), each cell is connected to a pair of complementary bit lines (effectively both Q and !Q), and a differential amplifier is used to sense the state of the selected bit.



1 For details, see Why are NAND gates used to make AND gates in computers?