I've had a total of four five 6 strings over the years (my usual default is a 5), not until the last one did I really gel with any of them. Whilst I still play 4/5s and definitely feel more comfortable with those, the 6 feels like i'm wielding more 'potential' with what I play. None of that applies for the usual covers, but even when it's Dream Theater I play at home to give myself Carpal Tunnel Syndrome - 90% of it can be done on a 5.
However, my GAS has swung very much to 6 strings recently, they just look better in my eyes.