I know nothing about pellet grills. However the major deciding factor in anything I buy new is that it is "Made in USA".
If your buying used private sale it's not as critical in my mind. So if they're both American made, I'd take the one with the longer warranty.
Primo XL, Pit Barrel Cooker, Tiernan SOB, Mini WSM, Big Green Egg Mini via Craigslist, 5 others, Black Thermapen