There are plently of differences between BDR and SPF most are subtle because if either one drove by or was parked in the street it's still a cobra.
However, if fit, finish and detail is important to you as the owner then go the SPF.
I also note that there is more passanger width in the SPF due to the shape of the centre console; now I can't recall footwell length but sometimes depending on your actual body size the width is important as length.
I have not driven a BDR but did go for a ride and I was impressed with ride and handling of the BDR although it was SB not BB that I'm used too.
Some details I have noticed are:
SPF has double skin hood
The air scoop and rivit detail are not right on the BDR
Detail and finish around the engine bay and proprietry moldings around the SPF create a feel of full finish, missing in the BDR.
No
oil cooler as standard on the BDR
Internal trunk detail fit and finish superior all round on the SPF
Dash board layup and gauges look home built on the BDR
The seats are not as good as in the SPF.
The standard wooden stering wheel looks cheap on the BDR
I'm still not sure about the chrome side pipes as opposed to Jet coat on SPF