I'm not sure if that's strictly true, or not, but here's my reasoning, and someone'll be sure to correct me if I'm wrong. (*shouts*
Famine!!!!)
Example:- Entering Rome 2hr Enduro in a fully modded Mini Cooper. I know it'll get thrashed by the Clio Sport V6 and Griffith 500, but it takes 25 reloads to get a "random" field, without either of these cars in, which is then possible to beat in the Mini.
However, entering the same race again in an Alfa 156, tuned enough to keep up with the Clio & Griffith, the first field I get has neither of these opponents, and the race is a solitary 2hr affair with no real "racing" involved.
It applies to Cote D'azur, for example, as well, if you exit and enter the race (or reload if you don't want to waste days!) numerous times, you can come up with a field without 787B and R390 LM racecars. Its then possible to win the enduro in one of the many Rally cars, or a non-race car with moderate tuning.
So many of the races are "one-horse" races, due to the AI selection, that its often more rewarding to select a field where the obvious faster entrant is not present.
Trial Mountain 2hr is a prime example of this. The NSX, when its present, is head & shoulders above the rest of the other entrants that make up the field. This means you either need to pick a car which will run close to the NSX, and blow away the rest of the field, or you enter in something more competetive and hope the NSX is a no-show, which ensures a more eventful and satisfiying race. The Supra RZ and RX-7 RS make great opponents and generally run close together.
It just depends what you're after, if you're just after the gold in the race, and don't care what you win, or about collecting all the cars in the game, then make an informed decision based on watching the race preview, as to what the field will be, and go for the win in something that's guaranteed to beat the opposition.
If, however, you enjoy close racing, and like me, are a little masochistic

, and enjoy running the enduros just to see how close the margin of victory (or loss!) can get, by running in cars that no-one would really think stand a chance of winning, then there's much more fun and challenges in doing it, that'll make a 2hr enduro seem far from dull.
Welcome to the GTPlanet
Miniklobb enjoy your time here. 👍
P.S. if you need some ideas for entries for really close races check out the GT3 Write-ups section, there's reports from many of the drivers on GTPlanet about some of the best races out there.
