Hey bud, I've compared to the two and am currently transitioning into the YTK Rad Pro, non IG.
The IG felt quite a bit softer IMO. It feels as though the flex ratings should be flipped. The IG also swung quite a bit faster, (clearly because of the lower SW.) Overall it was less work for me to mod up the YTK Rad to the spec I like, rather then use more tape to spec up the IG.
It really comes down to if you are looking for a VERY flexy frame, vs a relatively flexy frame. Both are really comfortable, solid hits, it just depends on if you are looking to play stock or mod them up.
If you have any specific questions on the playability on either frame let me know.