Decoupling Capacitor Loop Length vs Loop Area
When considering inductance reduction, what is considered more
important? Reducing the loop length or the loop area?

Loop area is the most important consideration.
When the wires are close (forming a smaller loop area) the magnetic field on one wires tends to cancel out the magnetic field from another. That reduces loop inductance.
If you use this parallel wire calculator and mess around with values you'll get the gist.