In my opinion, there is also the fact that some boxers' ears are more suitable for cropping than others. In those who are suitable for cropping, if left uncropped they will not lay properly and get the "fly-away" look that many people don't care for. This is because these pups will have a pretty erect base of the ear, and the flap will just go all over the place. (Disclaimer: I'm not saying *I* don't like it, but I know folks who don't).
Just as you have boxers whose cropped ears never stand properly, in spite of diligent taping, you also have boxers whose natural ears will never lay properly, in spite of tapings.
What I did was have my dog looked at by a boxer breeder and a vet experienced in boxer crops and they both said right away that her ears were very suitable for cropping. I could tell you, as young as 10 weeks or so, her ears were going all over the place (they were on the thin side). So when I went ahead and did the crop, they stood very quickly... I only had to tape for a couple of months before they were standing perfectly, even with the long show crop. (You can check out her ears in my gallery). Because hers stood so easy, the discomfort was very minimal.
All that being said, I don't know whether or not I would get my next boxer's ears cropped or not. I would ask for advice from the breeder I get the pup from, and ask an experienced vet whether they think the ears will either lay nice or stand nice and go from there.