I have had my YS640 for about two years and did a lot of research before dropping that kind of money. If I had to do it again I wouldn't hesitate to buy another Yoder.
1. As Red has mention with the Rec-Tec, the Yoder is hotter on the stack side, the difference is that with the damper, you can adjust how hot you have the pit from side to side.
2. As for space, when I smoke turkeys or chickens I always spatchcock, they take less time to smoke and I can then put the birds on the main grate and put other stuff on the 2nd shelf. I can do six 10 pound Boston butts on the bottom grates, a half dozen racks of ribs on the top shelf and still have room for ABT's and moink balls scattered around.
3. As for over night cooks, the longest I have run my Yoder was 26 hours. Over night was not a problem since I filled the hopper all the way before turning in and still had a good amount of pellets in the hooper the next morning. Yoder specs say the hopper will hold 20 pounds but in reality, I have filled it to the top and it can hold 30 pounds. I have no idea how many pounds it burns an hour. I was never interested,
4. Support - I have no experience with other companies but I ca tell you from personal experience that their support is one of the best, if not the best. First time I put in a support ticket was on a Saturday at 6pm, within an hours, Herb from Yoder support was on the phone with my, calling from a restaurant while waiting for his wife to meet him for dinner. In 15 minutes he had me working. As someone who never owned a smoker I probably used their support more then most but each time I emailed them, I always received either a call or an email that same day, hell Don Cary who owns Yoder and ATBBQ called me one night to help me through a problem, which was not a problem but my dumb move.
Support is a big thing for me, I have been in IT for 20+ years and we respond to server and network issues 24/7/365 and have clients world wide. Our clients pay some big money to have that kind of support, in the 4 and 5 figure range, per month. Yoder charges nothing.
Also, just recently Yoder offered a reinforced deflector plate to all YS480 and 640 owners for no cost except for shipping. They have made a few upgrades that were not free but could be ordered and installed by YS owners that improved the current design. I know of no other company that bends over backwards to improve their product without having to tell us that our smokers are obsolete and to get the upgrade you have to buy a new smoker. Additionally Yoder has a new two piece deflector that now has a removable plate so we can get to the fire grate and client it out without having to remove all of the shelves and deflector place. Just pop out two shelves, list the removable plate and we have full access now.
One more thing, my YS640 sits outside on my deck, hasn't moved in 2 years and only covered by a heavy cover. For the past 18 months I have had the thermal jacket on it. I took the jacket off back in December just to see how the past was doing and I had no flaking or no rust. Not sure if it's the newer models but I have ever seen a problem with paint and mine was built on 01/04/2014.