Simply put, the lighter the better. I guess that makes it a personal preference.
I tend towards rods that are lightweight for their line weights so in the same token seek lightweight reels to work with them as a tuned unit. When you get both to work in harmony they are forgotten and become an extension of your arm.
On the topic of balance, I was told some of the old Pflueger reels had a compartment in which you could put splitshot to help balance the rig. If that is true I liken it to taping coins to a record player tone arm to make the music sound better. Just as adding weight to the tone arm was hard on the stylis and record grooves I imagine swinging extra weight around over thousands upon thousands of cast might just take a toll on elbows and shoulders.
Even if someone says casting heavy rigs builds character and muscles I'll say that the lighter the more pleasant the experience.
Consider that even going back to the 1930's weight was considered a challenge to be tackled which caused Winston to come up with a device that allowed them to make hollow-fluted bamboo rods to reduce weight.
Photo from Tom Morgan Rodsmiths.