Is there really a big difference between ETC devices?

My car came equipped with ETC so I never shopped for an ETC device before. There are so many different ones. Some are cheap, some are not. About a year ago I bought an old car (1980 Chevrolet Monte Carlo) as a 'fun' cruiser car. I finally want to get an ETC device installed but I have no idea what is the difference is between the expensive ones and the cheap ones. I look at the description and I don't really see much difference. Why not just get a cheap one?

by zenki32