[DonC]

The primary difference between ERA and Superformance lies in how much individuality you want reflected in your Cobra. Both are undeniably great cars but ERA requires a lot more individual thought when you order it.
I spent the better part of a year researching both cars and in the end went with ERA simply because I could get the car exactly the way I wanted it right out of the gate. The amount of individuality available from a company that builds one car at a time can't be matched by a mass production supplier. The only trade off between the two manufacturing concepts is the amount of time needed to produce the car. Getting exactly what you want takes a little longer and a lot more thought than just picking "one from column A and two from column B".
Both cars have options lists but the ERA list is staggering in it's coverage.
Build quality for both is top notch but being able to talk directly to the individual who put your car together makes any questions you have a lot easier to resolve. There's no substitute for that aspect of the ERA build.
To my mind the whole thing boils down to how "special" you want your car to be. ERA can supply you with a car at any point in the build from a pile of boxes on your front porch to a complete car ready to drive away from the curb.
It's up to you to decide how involved you want to get in your finished product. While Superformance isn't a cookie cutter car there are still aspects of the build that are "standard".
The final decision for you is how much knowledge you want to acquire about what's going into your car. You can take the time to build an in depth understanding of what you've got or go with what is provided by someone else.
You can't get hurt quality wise with either car but, for my money, the ERA is the much more individual of the two.
I could go on for a long time about the what's available from the elves at ERA but, for me, deciding for myself is what it was all about. You can take what's there or get into it up to your elbows.
DonC