Balance is a soapbox topic for me. It's so critical to how a player perceives the cue. Too front heavy & it feels like you're pushing it. Too back heavy & you're pulling it. It's very much akin to wheel caster. Negative caster, like rear balance cues, makes steering very difficult to control and subject to abrupt, unintentional turns. Think shopping cart. Positive caster gives much more predictable control but at the cost of limited range. Somewhere just positive of neutral is your Goldilocks balance that allows for plenty movement but well within your control.
That's what I strive for in every cue. It means beginning a build with balance in mind and remaining cognizant of it throughout. I know what my finish, bumper, hardware, joint pin, etc. weigh. Those are statics, set in stone, meaning I have to design around them. I use shafts between 3.7oz & 4.2oz on 95%+ of my cues for the same reason, to keep a level of consistency that allows me to easily reach my desired balance. A set of shafts for a cue are perfectly weight & tone matched so that each will not only feel the same, but will balance the same. The set is chosen specifically by weight for the purpose of balance.
Hitting that Goldilocks zone means the difference of a player being in awe of the cue or being indifferent, or perhaps even disliking it. Think about that wheel caster. A player trying to use draw but can't, or a player missing badly with an open bridge. Is it really his stroke or is it his cue has negative caster? How about a guy who can't seem to ever gauge table speed? Maybe because he's always pushing the cue like a wheel barrow through the mud. And then you hear about a cue where the guy says he can't miss, like the cue knows what to do & does it for him, as if he's played with it forever. That's because he got a properly balanced cue.
Now think about the so many cues you see advertised with two+ shafts that have different weights. That's a pet peeve of mine. With cues like that you hear that one of the shafts is awesome & plays great, while the other(s) is/are ok. The shaft isn't better. It's merely the correct weight to give proper balance while the others are not. Little things matter. A quarter ounce here or there can have a big impact on how your cue is perceived by the player. It's not rocket science but it is science and is worth the effort to learn. That's my rant for the day