I chose Holan Nomada Pro II panniers and top box for my 2016 GSA
http://holan.pl/en/. There were a number of reasons for that. First I wanted the overall pannier width to be minimised or at least narrower than the standard BMW boxes which IMHO are just too wide for traffic filtering. Holan do 3 sizes and I chose the 38L side panniers which for me are a good compromise between width and capacity. Second I wanted the RH pannier to have the cut out for the exhaust rather than sit completely outside the exhaust as most non BMW panniers seem to do, again to reduce width. Holan were the only manufacturer to do this I could find. And third Holan offer a range of different finishes for their boxes
Overall I'm very pleased with the Holan products although their customer service left a lot to be desired. Basically dont trust their delivery times and dont expect them to communicate with you when they are late