yeap. i think that the cars are greatly modeled and all but....
alot of people dont know but the cars from FM3 that was in FM2 was exported to FM3 (the outside body only, they didnt had an interior). they didnt even change the UV Mapping of the cars, just add the interior and remake some minor things in the body. and the alot of cars from FM4 was actually modeled for FM2 ...no UV mapping changed again or re-modeling, only add new lights mechanics.
ofcourse that FM3 and FM4 have new recently modeled cars. and you also can notice that they have less Mapping bugs than the older ones
so yea, we have cars from FM4 in FM3 ( the exactly same cars)... and most of them comes from FM2.
UV mapping bugs had being annoying people for years. i will give you 1 example now that i remember clearly from FM2 to 4
R34 skyline mapping bug ( the left sideskirt is mirroring the right side. the front lip (that down black part) has being mapped only on the sides)
there is tons of theses mapping bugs on the older models. they are pretty annoying for those who makes graphs desings
Forza Motorsport 4 will feature 500 premium cars on Disc 1 and 2. Its roughly 300 cars on Disc 1 and 200 cars on Disc 2. There are approximately 320 cars carried over and updated from Forza 3 as well as approximately 90 cars carried over and updated from Forza 3 DLC. The remaining 90 are so cars are new to Forza 4. Starting at launch, we are currently planning to add ten cars per month via DLC Add-On packsthis will include the Day 1 American Muscle Car DLC pack (free via a code to LCE buyers) as well as new packs starting in November.
I think you should buy FM4. It has all the DLC cars from FM3 (except Porsche's) included on the disk and there are many more cars that are all new to FM4.
I personally think F4 crushes F3. I traded F3 in about a week or 2 after F4 and dont miss it at all. There are a couple tracks I miss but other than that F4 has almost everything I want from the Forza series.