I was using a 12' radius and just recently switched to a 13' with a neutral pitch, and for me, I love it. I had switched to a 12 with a +1 pitch last year. At first it felt like I was losing some agility in turns, but after a while I stopped noticing. Now, it feels like I've gained agility because the extra stability lets me hit turns and crossovers way harder. Since I went up to the 13' radius, I also found I could loosen my skates around the ankles for more mobility and better feel for my edges, which I feel has translated into longer strides and more power. Honestly, right now, it feels like I turned back the clock ten years and found my old legs again.
Now, I'm a smaller guy in junior skates so ymmv with senior skates. But like I've said, it's been nothing but positive for me. I've even been playing with the idea of a 14' radius.