Accuracy and repeatability.
For a power supply, I look for the fewest rails that can still handle 1.5 times the greatest single rail load anticipated (continuously).
I'm old fashioned about my optical drives. I want the one with the lowest seek time and highest bandwidth that still has jumpers to hardwire the master/slave configuration.
Monitors: A bit more complex: Generally, anything with 1000:1 contrast ratio or better (your eyes generally can't distinguish any larger ratio). With LCD monitors I look for a native resolution that is between 60-70% of what the vireo card can do. Speed of 6msec or less.
As always, just my opinion.
Jim