Quite a bit of difference actually. I found #3 works best for my shotgun, close enough to #4 to not split hairs. Lighter recoil, better spread pattern, and not a single hiccup yet though the buck is gettin outrageous at $6 / 5 shot box, when I can get a 25 shot box of #3 or 4 for the same price at Dicks, just bought Rem Nitro's last week in 4s.
Definately right weapon but if you reload might I recommend the military's answer? Broken glass, its very lethal and when it hits a wall rather than destroy it the glass turns to powder and can easily be swept up.