Although I am not a fan of ol' Shel, himself, I do know that there are an incredible number of people who think he can do no wrong.
To that end, there will also be an incredible number of people to whom the CSX serial number will mean something...and that something may well translate into additional $$ at resale time.
IMHO, the ERA kits are the gold standard in our industry, not the Shelby products. I have seen one up close, it has some very nice features (one of which I particularly like is the way in which they finished off the cutout for the headers at the bottom of the front fender), but in the end it is just another replica in my eyes, even if it does carry the Shelby name (that doesn't mean he necessarily has ANYTHING to do with the production of the cars, other than perhaps selling someone the right to use his name).
You're wise to do some research....good luck in making your decision!
Cheers, Dugly