I'm going to put the fanboy in me aside and look at this from an open perspective.
If you look at forza and gran turismo they have different pro's and cons.
in forza you had a nice paint scheme and all cars were premium (literally) but there was only 400 You could swap motors and do other things. As disappointed as I am that some of my cars wont look as nice or be modded the same in GT5, the list is still there.
The graphics and the physics are far superior to that of forza, how people use to complain about the tire screech in the GT series, have you listened to forza? sounds like someone strangling a rooster, and it happens even if you ever so slightly turn the car. Don't get me wrong. both are good games, both have their pro's and con's, but my personal feeling is as a simulator and what you get with 60 dollars, I'd have to say premiums and standards with real weather syncing/snow ruts/even air density? all that with 1000 cars, premium or not, wins in my book, but that's just me, we're all entitled to what game we think is better, but even tho GT5 does feel unfinished, there's just too much there to even start, and it's apparent why we got a bad end of the stick.
I figure it like this, if we lost the weather, and we lost about 300 of the cars, the data for the cars/weather could of ended up giving us about 600 premium
cars, I'm not sure I'd be willing to sacrifice the weather for that.
But either way, I just feel albeit it has a very incomplete feel to it, GT5 gives you a much better experience overall.