A MK1 is a lighter car and certainly the tin tops were quicker. A MK1 CAB is heavier, having to be strengthened cross ways and underneath due to not having the support of the roof. Probably about the same, talking only a few seconds in it. Depends what you want, you want something to out run everyone else then a CAB aint for you, it is nippy but it aint meant for speed its meant for the summer and chillin with the roof down. if you want speed and if your going for the insurance of the GTI CAB then perhaps a 16v MK2 is what your after insurance wont be much different.