X2, I have both as well. I find the Klim has much better ventilation and wears cooler, while the 509 I find really warm. 509 is a bit lighter, and has a much better breath box. I struggle with the Klim breathe box, getting it to sit right and seal properly. For warm weather though, I always wear my Klim, for cooler, I'll rock the 509. All depends on what fits your head best.I have both, Klim and 509. The Klim is better quality but the 509 has better vision out the sides and a bit lighter. You'd have to try them both on to make a decision for yourself.
I didn't care for klim, and ended up going with 509 a couple years ago and liked it. This year I'm trying the new Motorfist.