ITX 10 is between steel & lead, in performance. ITX 13 is heavier/better than lead performance.
ITX 13 is basically their own version of Hevi-Shot.
I have never used the ITX but have shot lots of HeviShot and straight TSS. If the ITX 13 patterns good (out of your shot
, it should work great.
I, personally, would not pay the extra for ITX 10 unless I was shooting it out of older, non steel shot approved gun.