Not sure about the gauge of steel. But for small family of 2-4 the 590 is plenty. Now if you have a fair amount of dinner guests from time to time, then maybe the 700. Otherwise they function pretty much the same. I occasionally have 11 (rarely lately CV) and have always been able to do enough meat and taters for the bunch with the 590. Takes up a smaller space, uses less pellets cause it is smaller, and I think it heats up to above 500* a little easier. On the other hand, if you anticipate occasional bigger cooks, or just like the design the 700 is one of the best bangs for the buck out there IMO. I think gauge of steel is a non issue, as you will never wear out the SS on either. Also, because of the design, I prefer the back side vents on the 590 as the air draft is more evenly distributed to both sides?