I have the MMIF which I picked up a year ago. Both are awesome pits. Both are fully insulated and are built like a tank. You lose approx 12" of cooking grate with the MMIF which is the size of the internal firebox. You only lose the space on long cooks as you have the extension on the firebox. For grilling or shorter cooks (chicken, ribs) you would still have the full surface to cook on.
I have 2 levels (grates) to cook on or hold temp on. It has 2 stacks so you can cook on the top level at 225-250 and hold meat on the bottom level at 170. This is done by adjusting the stacks. That's what sold me on it as we cater at times.
I use a guru on my MMIF and it will hold temp like a rock for 15-20 hrs with a full chute of fuel. I use briqs and wood when I cook. No reason why you could not use only wood if you wanted. Like any offset, once you get the temp dialed in and your vents set it will hold great using wood in the MMOF. The firebox is insulated as well in the MMOF.
With the MMIF you fill the box from the top. I have all the room I need with the MMIF. So the 12" you lose with the firebox extension is minimal. I could grill 80 steaks on the top grate alone as I bought the charcoal grill pan. The MMIF will hold alot of food. It's the best built smoker I have had. Bill took us for a tour of the shop when we picked it up as well and he is a great guy. Great smoker and great company. I will have my MMIF for a long long time.
If you want any other info on it send me a PM and I would be glad to answer.
www.thunderroadsmokehouse.com - Stump's Prince - Peoria Cookers Meat Monster - Lang 36