They both shoot about the same. I like the balance on both lengths equally, the 8 being maybe a little steadier at arms's length. The 5 1/2 bbl is easier to draw and move from target to target. Both have their advantages. I would get two the same for CAS just so no matter which one you draw, it will feel like the other one. For CAS I use 5 1/2's (actually one 5 1/2 and one cut to 6 but they feel almost identical).