A fast story. Parica was in the pool room making games. While they were talking he was banging balls around with a house cue that had been laying on the table. They came to a spot, something like the 6 and 7, I don't really remember. Then the guy says, you also have to play with that cue and Parica agrees. After losing like two sets Parica wants to use his own cue. He even offers to up the spot if he can use his own cue but the other player says no and they play one more set with Parica losing again and he quits. Turned out the cue was the biggest part of the spot.
The only reason one player plays better then another is, they can do things the other player can't do with consistency. If they are handicapped by a cue they can't play as well with, some of that edge is gone.
Much different then just giving up a spot. When you give a spot you may still lose, but it will be because you just can't overcome the spot, not because you can't play your speed.
If you are talking high end cues it is not so important. I have seen Keith play in a tournament with a different borrowed cue for each match and play perfectly. I remember being in a pool room and Keith was matching up playing one pocket. Keith was a little drunk and I think the other player thought he was going to take advantage of him. Keith looks at my wife sitting there with her case and asks if he can use her cue. He proceeds to rob the guy, drunk with a borrowed cue. So I guess there are some exceptions. The end of the story is, he drops his money all over the floor and doesn't even see it. No one makes a move or says a thing, they are all just going to steal his cash. My wife collects it off the floor, straightens it out and gives it to him, he had it in a big wad, like $3000.00.
