It is possible that the QRX will slightly out volume the KW's.
Depending on your needs, most small venues indoors (<300) can be handled by a single pair of KW181's.
Each KW181 can be handled by a single (strong) person (I can move my PRX618S-XLF by myself, but it is cumbersome).
The QRX's are much heavier.
If moving them isn't an issue, I suspect that the QRX's can be made to sound slightly better (depending on your expertise in using the cross-over, eq and limiters).