I own two of the grills you are considering and do think that for the bucks, it is hard to beat the Green Mountain grill. Here are some of the advantages that sold me on the grill.
With over 13 inches in head space, you can easily double the capacity of the cooker with a full second grid. Enough space for a case of butts.
Then again, you might like a rotisserie
Hot breaded wings
Again, with the 13" of head space, you have room for some rib tips over your pit beans.
It's also pretty easy to set the cooker up for high temp grilling at the tip of a flame.
I also like the low temp of 150 degrees for my jerky and the upper end at 500 degrees for my baking.
Pizza on a raised hearth.
Focaccia bread and all of the above done on the Green Mountain grill.
It also cooks quite well in the Winter time at the lower temps.