I can comment on the Blazin, as I have a Grid Iron at home, one at my buddy's lake house, and my inlaws have a Grand Slam, & I have cooked on them all.
I've probably ran about 400-500lbs through mine at home in the last 5 months.
Grid Iron:
Grill Area: 702 sq. in. ( 36" x 19.5" )
Including Inside Shelf: 310 sq. in. ( 31" x 10" )
Total cooking surface with shelf - 1012 sq. in.
Hopper Size: 30lbs.
The pull out fire pot is the cat's meow for a couple reasons:
1) If you ever experience a flame out, you can pull it out, get rid of any excess pellets, put it back in and fire it back up w/o removing all the food, grates, grease pan, heat deflector, then vac it out & put it all back together.
2) Quick and easy cleanout before each cook or in the middle of a super long cook.
3) To make starting a bit quicker, I put about 1/4cup of pellets in it before each cook after I clean it out.
4) If your ignitor rod goes on the fritz, just pull out, add some pellets, light, shove in and you are up and running w/o having to go through everything listed in #1 above.
The controller on the Traeger is different. Blazin uses an Ortech 100. It is programmed a bit different I believe. After I got some seat time w/ it, I have got it down and rarely have trouble w/ it. It is true that if you set to 180* when you open the lid, it will change the duty cycle to 50% no matter what it thinks the temp is (when you open the lid for an extended period of time and let the heat out, the controller will think that the temp is lower than what it is set at and will dump pellets in at 100% duty cycle until the lid is closed and the temp goes back up, plus any overshoot from the fire pot blazing away. I think that this can happen w/ almost any pellet grill to a point)
They are American made in Beatrice, NE.
As for searing, Blazin Grill Works make sear kits that seem to work quite well.
Also, the Blazin has an optional hood insulator kit and also optional roller grates. I have not purchased all the above yet, but plan to.
Blazin also gives you a ton of different powder coat options so you can customize the color.
Their shipping is pretty cheap from what I hear, maybe because they are only selling them factory direct now.
The Blazin also has a 30lb hopper and a rounded auger rod so that it helps w/ pellet jams.
They are built like tanks, second only to the Yoder.
What I would change on my Blazin Grid Iron... Well for one thing, I would like for the standard top shelf be on a slide track rather than mounted on peg holes on the back side.
I will probably swap out the controller for the SSII when they are available, but that is only because I like gadgets and want to hook it up to a Rocks Stoker and have a full internet interface...
Have fun researching. I would try to find a store w/ the different models or find somebody that has each one so you can touch and feel it to get a better idea of each too.