Having owned both:
The Yoder is built with heavier material - *BUT* that does not meant that it will "hold heat" any better than a thinner pit. Steel is almost "thermally transparent" - it soaks up BTU-s then passes then right thru to the outside. So - thicker is not an advantage. In fact-the thicker the steel-the longer to heat up the pit! ( You must overcome the cold thicker steel using more BTU's than thinner steel )
My Yoder pit would use 1.25 to 1.5 lbs of pellets per hour at 250F. If I turned it up all of the way - it would burn 5 lbs. per hour!
The pit design - with the rectangular fire pot on the extreme left makes it difficult to- if not impossible to have even temps across the pit. That is not necessarily a problem - unless your objective is to load the pit - and leave the door closed, and not have to move meat around...Bearing in mind that it can take a pit 20 minutes - sometimes longer - to recover from BTU loss from opening it and fiddling with the cook.
The controller is "proudly" a Yoder design.....And, that sounds good at first. But - they continue to have firmware updates ( those must be installed by you waiting for a programmer to arrive - which can be weeks. Then you have to remove the left end of you pit, and plug this thing in correctly, and not short out anything...P.I.A. ) - even now after the pit has been out on the market for approx. 3 years. Why? Because Yoder has always been an "in-house" pit builder and has a great history in offset pits. But - when they moved into pellet grills, it is my opinion and experience that they really should have reached out to an already successful design - built by companies that know pellet grills....There are 4 companies that make pellet grills which use the same controller manufacturer - who will tailor their controller to suit the pit design....
Pellet grills operate under significantly different ideals. We can't say different physics, or principles - but...ideals. Like a different manner of managing airflow/air throughput. The very method of feeding or fueling the fire. And on...and on.
In short - the Yoder controller is not where it needs to be - in order to compare favorably against other manufacturers. The body of the pit will out live you. It is the heaviest built unit on the market. But, there is more to a pellet cooker than just heavy metal construction....
I think you should also consider the MAK 1- Star. There are several users of them here - and it is a great cooker. ALL American made too....Sparky1 and Tenthunter - and others can give you input on that one.
Synopsis:
What I had hoped would be reliable, and temperature steady...well...it just wasn't. And it became an issue to feed the beast if I wanted to run it above 350F.
So - I sold it. I now own both a Rec-Tec, and a MAK 2 Star General. Love both of them for different reasons. If you are looking to spend the amount of money that A Yoder YS-640 will cost - I recommend the Rec Tec. .
If you want to budget for a little less - the Rec-Tec is probably the best deal on the market for "features per dollar". Lots of space, a light in the cook chamber, 40 lb pellet hopper. And - just looks really nice. Even my wife thinks it looks nice on the deck. And the controller is top notch. Spot on temps. And - all of the key internal components are made for thick stainless steel ( fire pot, heat deflector, drip pan..)
Lastly - about the 500F top temp of the Rec Tec vs the 600F of the Yoder....
If you put Grill Grates in the Rec Tec - it will produce sear and grill marks as well as any cooker. You will not see any real difference in the cooking. I do steaks with beautiful sear marks all of the time on the Rec Tec.
