Insulated vs uninsulated fireboxes

I dont have an insulated FB but I've cooked on some and I'm a Fan! Esp if it's on one of Muscrat's build.

Refractory Lined Firebox

Even though my firebox is 1/2" steel, the pit was super hot when in use and I was worried about it damaging the brick on my house (even though the pit is about 3 to 4 ft away from the wall on the patio). I then lined the firebox with refractory from a testing lab that is owned by a friend of mine. I also purchased a 1/4" steel plate and installed on the top rack of the firebox to deal with the flame impingement on the top of the firebox. The outside of the firebox runs much cooler now and no longer have a problem with paint peel. I suppose I can get internal temps higher now, but really not too big of a difference in the way the pit cooks.

You don't lose as much heat radiating off FB so cooker is more efficient - smaller temp swings and responds faster if you bump temp.