Surely they are being used for completely different purposes. High density 737-800’s compared to scheduled CY A320’s.
The Eurocypria 737-800’s were perhaps chosen to fly into airports with no baggage loading facilities etc.( i.e 737 loading is nearer to the ground)

Agree. Eurocypria is a charter airline so needs an aircraft to suit high density, high rotation needs (probably the same reason why Ryanair chose the 738) whereas Cyprus Airways scheduled routes.