BDR have improved VASTLY as they have built more!!!!!!!! As far as SPF from 1800 on very minor changes, but they weren't needed, the car is as solid as a dump truck. I agree the difference between a 2009 BDR and 2014 BDR should be noticeable, the difference between a 2005 and 2014 would be huge. Heck the 2005 had slip fit side pipes. the difference between a 2005 spf and 2014 is minimal IMHO.
Bottom line is the Cobra market is probably getting close to saturation. Sure you find a true stud like me (lol) buying them in my 30's and 40's but the majority of owners are
60 plus years if not 65. Everybody regardless of age still loves them but most don't have the drive to own one.
BDR does a great job with offering custom builds, mod motors, coupe tops? but is it BDR or Vintage. If I were to buy a new BDR hands down it would be Vintage. I think their service after the sale would be exceptional, not that you should need it but from my experience there is a lot of sorting with these things which mystifies me since you buy a new GM or Ford which is exponentially more complicated and you don't have issues for the first 100k miles or
oil leaks......
If you are buying and attempting to cut looses or break even buy used. BDR I would guess anything above chassis 800? not an expert anymore on BDR. SPF anything above 1800 or even 1000 and do the bolt on upgrades yourself.
If you can dip your toe in the water for $35K on a BDR no brainer if its clean. Drive if you like it and want a SPF or ERA you tested the waters. If I were spending 50K plus I would look hard at a used SPF for the most part it isn't going to depreciate any further. Sure there is always the chassis 250 with a bare 351 in for 40???? but if I were spending $50K-60K on a used SPF it would have a 427 be it stroked or FE and be done with it. Remember in the end regardless of what you buy it takes up the same space in your garage, you have insurance and registration, fixed cost are the same.