Match the forage size! This time of year they are eating the stunned or half-dead shad rolling along the bottom. Bigger size will do great!
Later in the summer when the shad have spawned and the fish are chasing shiners or silver dollar shad the 3″ moxi rocks! But if they are feeding on perch or bigger shad, forget the moxi and go for a 4-5″ grub!
The other time to switch to the 3″ is when the fish are short hitting the bigger ones.
My PB (personal best) walleye came on a white 3″ moxi, and last fall I caught several 10″ saugers on the 4″. So the old saying big bait big fish doesn’t ALWAYS work.
So get both sizes in an array of colors and you will be set! Best colors for me have been white and chart/white core.