Newbie with Backdraft Interest

[Ace23]

Any advice on a specific car build number or range of build numbers to start looking at when looking at used cars? For example does a builder keep their own numbers or is the car serialized based on the actual number of BDR cars that have been produced? I have heard from a few BDR customers and a few have had multiple cars and say that these cars have continued to approve. I was advised to look into cars after 2009 but that is personal opinion and I was not provided with any facts on why the cars 2009+ may have been improved.