They definately are not worth the pain. My 12ga patterns better with 3" shells
For the brief time I carried a 3.5" gun, I still shot 3" shells for that very reason. I patterned it with Longbeards (both 3 and 3.5's) and HeviShot Mag Blends (again both 3 and 3.5's). With both brands, the 3" version patterned better than the 3.5. I eventually settled on the Longbeards because they were close enough in performance that I couldn't justify the higher price on the HS shells