You're confusing what I was saying. In an HDMI situation if you use a cheap cable and the picture and sound are fine, buying a more expensive cable isn't going to change anything. With HDMI in particular, if the cable is failing you'll know right away with either a poor picture or sound. It won't have the gradations that were possible when pushing an analog signal around - i.e. the picture looks could, but it could be sharper with a better cable.
I'm not sure why you brought ethernet into the mix, but generally you're talking about much longer runs than HDMI and it's often not as easy to see when your are losing packets without specifically checking if you are dropping packets (IMHO poor network performance IS failing outright, but not as easily seen as a bunch of blocks on the TV). Even then, the cable you use is either delivering all the packets or it isn't (up to an acceptable level of errors/loss for the length you are running). Delivering a stronger 1/0 isn't going to change anything as long as it's strong enough for the receiver to differentiate. That's where it either works or it doesn't comes from.
I'm not sure why you brought ethernet into the mix, but generally you're talking about much longer runs than HDMI and it's often not as easy to see when your are losing packets without specifically checking if you are dropping packets (IMHO poor network performance IS failing outright, but not as easily seen as a bunch of blocks on the TV). Even then, the cable you use is either delivering all the packets or it isn't (up to an acceptable level of errors/loss for the length you are running). Delivering a stronger 1/0 isn't going to change anything as long as it's strong enough for the receiver to differentiate. That's where it either works or it doesn't comes from.