I always wanted a GS, but didn't buy one because of the height.
I purchased a R1200R last February, because the sales guy (new at the time) didn't know that the GS is available with lowered suspension.
BMW Australia also doesn't promote it very well on their web site or in brochures.
IT is all about personal preference and what feels comfortable and safe.
I ride my bikes in traffic and stop/start a lot, therefore I want to feel safe when stopping and don't want to slide on the seat to make this happen.
I rode the "normal" GS and it is just manageable, but it never gave me a good feel.
I took delivery of a GS Rallye with low suspension three weeks ago and it feels right.
The bike still has the suspension in low setting, when riding in traffic.
I never considered lowering a GS, as it involves cutting the centre stand and side stand and also is not a cheap option.
The factory option was only AU$250
I'm 167cm in height, whatever that is in your system