Being a ham radio operator, I know a bit about twinlead and coax. Twin-Lead is cheap and works great for long runs, and its' attenuation levels are much, much lower. Having said that, it is a pain to run - it shouldn't touch anything (keep it off the roof and ground, and where it enters the home) and you need to be careful around metal or it can become imbalanced (needs to be minimium about two to four inches away from gutters, etc.). It won't be destroyed, but if you break those two rules, its' benefits go way down. It is also harder to ground properly for lightning protection. The rise of coax is due to an abundance after WWII surplus, it is easier to run (it can touch anything), easier to ground for lightning, etc. However, the nice thing about twinlead is it is easily spliceable, cheap (if you can find it) and works fantastically.