IMHO, Frankfurt and area has a better FKK scene than Berlin in terms of variety. Best is Zurich in terms of beautiful women. But more expensive.Berlin
However, I find Berlin to be much more interesting than FRA for everything else (non-P4P stuff) like food, scenery, vibe etc. Very cool city. I now only go to FRA FKK's if I am travelling and then I always try to get a 1 or 2 day stopover in FRA for FKK action and to go to a public sauna park called Taunus Terme in Bad Homburg, near FRA. What used to be my fave FKK Oase in Bad Homburg has gained a reputation of lazy, over priced service.