Hello Tibbs, I actually designed the M1 so I can shed some light on the differences between the grills mentioned. We are new so I understand there are not a ton of our grills out there, but we are selling them steadily so you will start to see more and more of them throughout the year.
The biggest difference between the M1 and the other grills mentioned are its grilling and smoking capabilities. The M1 has a fully adjustable grate for grilling and searing. You can put your water pan on this grate for smoking and position it where you like. You can also use this grate for a secondary smoking rack.
The firebox portion of the M1 is in a reverse airflow configuration with a large slide out firebox basket. It handles wood extremely well and it's very easy to maintain and smoke on. Since the firebox is self contained on the bottom, you have a much deeper cooking area. I only stick burn on the M1 and it's a dream.
If you want to grill, there is nothing to remove. It's all there. If you want to smoke, there is nothing to take out or replace, its all there. You can even have the firebox smoking with wood while you are grilling. It's very versatile.
Comparing the M1 to the Hasty Bake is really night and day. We get this a lot. The M1 is designed differently. The firebox is self contained and does not double for grilling and smoking. There is no baffle you have to slide in and out. You can smoke more food on the M1 if you use your bottom grate. The most obvious is that its built much more heavier. M1 is 10 gauge vs 18 gauge steel on the HB. Nothing on the M1 is nickel plated. If it's not part of the main grill (painted black), everything else is solid stainless steel besides the main handle which is stainless tube.
A nice addition is all of our grates are solid 1/4" stainless steel. No expanded metal (besides the firebox basket) and nothing is nickel or chrome plated.
Is it an expensive cooker? yes, but it is not cheap to make and worth every penny. There is not one thing we skimped out on in making this grill. So if customers are getting 20 years out of their well taken care of Hasty-Bakes, I can only imagine what they will get out of their M1. Only time will tell on that one.
I have seen SOO many grills over the years and my biggest issue with most heavy duty grills for less money is their fit and finish does not come close. Gaps in lids, fireboxes, doors, etc... The M1 seals up nicely and we pay very close attention to all of the internal and external welds. We do not leave any external welds visible on the lid and body. So every weld is finished down to a beautiful appearance. So sure you can buy a cooker to smoke more food on for less money and it might even be out of 1/4" steel pipe, but the attention to detail and aesthetic will not come close.
I truly believe there is nothing that comes close in the full capabilities of the M1. This is why I designed this cooker. It completely replaces the need of having a fully capable fine tuning charcoal grill and needing a very nice wood smoker. There is far less compromise with the M1. Unless you just need more cooking real estate and that is something we are designing right now. A larger version of the M1.