Just to add to Harry's comments and as someone who has just come out of a well fettled Griff 500, off the line they feel very similar. Above 90 mph (circuit conditions only of course) Griff felt as if it had a bit more poke. Could it be that the Griff shape is more slippery, it certainly looks it.
If you look at empty weights of both cars a Series 1 Aero is probably lighter by about 50kg comparing apples with apples (my Griff had aircon & pas). As Harry points out Griff's 340 gee gees (and subsequently 320) are optimistic, whereas I'd imagine BMW's 286 to be all there. On torque there's not much to choose between them.
Whichever way you look at it both cars are pdq and short of back to back standing qtrs with the same driver I doubt you'd find much in it.
All imho of course
Cheers
Philip
