There are several distinctions that need to be made in order to properly address this question. For one the make and model needs to be considered. Each such make and model have different rates of depreciation. Another is the age of a car made in comparison. You cite a two year old car, but the variables will be quite different if you buy one that is five years old, then one that is ten or two. Also a well maintained five year old car can easily also last 10 years, the time you cite owning of a new car.
However, in general, these are the things to consider in evaluating the risk:
1) Asset loss. If you own the vehicle to term, and sell, you will realize the loss of an asset. You buy a 30K car, and in 10 years it will probably be worth around 5K. About 2500 per year. You will lose less buying a 2 year old car, and driving it 8 years. To really avoid asset loss buy a 10 year old car and drive it for 3 to 5 years.
2) Being forced to sell prior to term. While there is probably not much difference in the asset loss of owing a new car 10 years, and owning a 2 year old car 8 years you might be required to sell prior to the term in question. Most often this will happen because of destruction of a vehicle. A loss in the first couple of years of ownership is especially devastating because of the rapid declining in values.
3) Higher ancillary costs. When you pay more for a new car, that sales tax amounts to something. Additionally you may pay higher insurance or licensing fees.
In some occupations or status in life you may be better owning a newer car. Salesmen who have to portray a level of wealth in order to make sales should drive only late model "clean" cars. The same may hold if you are single and on the hunt for a mate.
In short there are a lot of assumptions and variables one has to make. Very difficult comparison to make. However, if you save up and pay cash for a car, you know you can afford it!