The only comparisons that really ever made much sense to me for understanding root value is showroom floor to showroom floor, same track, same weather, best drivers (or same pro) for each. After that it enters la la land pretty quick where anyone can make whatever case they want with enough time and money. That's why for the 2012 GT-R vs. Vette the Hot Laps at Laguna Seca are quite telling where the car's stock performance envelopes are and the Z is pretty far ahead at a non-trivial 2 seconds/lap. However, roll up to your local street legals, and the average amateur in a GT-R is going to beat the average Vette the majority of the time I'd bet.
The racing I like is either spec, where the cars are virtually identical and over the course of a season you can honesty have a good idea of who the better team is (human element) because you've largely controlled for hardware. On the other end, and there isn't any of it any more, is profile spec racing, which says it just has to be within a certain footprint but otherwise you can do ANYTHING. That only lasted a couple years because Porsche prison raped everyone else.
The Finns have a fun ralley concept for working class people where it is dollar spec. The idea is you can run anything as long as you spend no more than $2,500 (don't remember the actual amount) on the whole car. After a race, ANYONE can look at your car and if they call bs you have to trade with them. Interesting idea.
As far as I can tell for the most of the real world in racing, it effectively comes down to a test of hardware because the drivers for the most part are so good, the winning margins are going to come from equipment.
This certainly seems to be the case in F1 where a recent dominating champion can move to another team and quickly be down the leader board.