Whats wrong with the stock seat? Time to just harden up I think and ride more!!!!
Just kidding, all references I have seen to both seats have only had experience with one of the two seats. I don't think I have ever seen someone who has tried both, nor had the money to spare to try both.
Both get good reviews, but if are going to try one, you will just have to pick the one that suits your style better.
Personally, I never had a problem with the 250's seat, easily putting upwards of 200-500kms in a day on rides.
My 650R is the same, I have no issues with the stock seat, and I have covered the same kind of distances on this bike. Everybody on Kawiforums complains about the 650's seat, but I have not had an issue.