Not sure why but I've always hated X100s but I love PX 6.5 and have played them for years. I've since switched to MMT 125 TX but if I had to go back to steel, it would only be 6.5s. I'm not overly mechanical but I'm a feel player. I always felt like the X100s were work to swing, but the 6.5s almost swung themselves. It might be the few extra grams, but I kind of doubt 4-5g would make such a difference. The 6.5s always made irons feel softer for me at impact as well.