Tim,
I think I understand your point. I still remember when I was doing "research" as a newby. But, there are a bunch of threads now dealing with this...and aside from ERA no-longer producing cars, not much has changed for a while.
In my earlier post, I made a brief attempt to categorize cars in a fashion that I hoped would be helpful to the original poster. Maybe it wasn't of much use, but...
As for Mark's suggestion of a rating system, interesting idea, but it would still be very subjective. Suffice it to say that any of the more original-styed mono chassis (SPF, Gelscoe, H-M, Gox, and those guys in New Zealand (can't remember the name right now)) would handle very much like, well, an original. Of course, one would have to consider advancements in shocks and tires, but they should all be more or less the same.
As for ERA, CAV and RCR, I believe they all have suspensions that are somewhat "optimized" for modern tires, so potentially they could handle better than the originals. This is also potentially true for any of the spaceframe cars as well. Realistically, few of us can drive well enough to approach the limits of any of these cars, assuming they are set up correctly.
As for originality....that could take pages. Suffice it to say that most of the mono cars are pretty close, some are very close, and a couple are spot on. The entry price rises exponentially as one attempts perfection. The devil is in the details, how much do you want to pay? ($75K to $500K)
All of the cars that come as rollers (the ones I've personally seen anyway..CAV and SPF) look pretty good right off the boat. Engineering and customer support...depends on who you ask, and what about. All of these cars are built to a price...low or high, and some corners have to be cut. Personally, I'm very happy with my SPF, and consider it a bargin. Other's may not think so, but it depends on your perspective. I once had a Kirkham Cobra, and it was an absolute jewel. Again, I thought it a bargin. But if you only had $40K to spend, it wasn't such a bargin. Again, perspective.
The other details...fit, finish, customer support etc. Most of these are at least somewhat subjective, and depend on how the car is purchased (partial kit, complete kit, roller), and on who does the assembly. I'm not even going to try to cover these. I would suggest you just read up in the respective subforums to get a (somewhat) unbiased idea of the different manufacturers. In the case of SPF, the manufacturer doesn't provide much, but there is a good bunch of dealers and owners that can help you out.
Everyone has to decide what's important to them, and how much you care to spend. Then, the choices become somewhat easier.
Ron