If you get a Blackstone, skip the 17 inch and go directly to the 22 inch.
The 17 works fine, but the 22 inch has 2 knobs and 2 burners, so you can cook 2 things at different temperatures.
You can cook eggs on one side, for example, and pancakes on the other side.
Plus, with the 22 inch, the grill surface gets up to temp pretty much 99.5% all over the grill, giving you more consistent heat and thus cooking. The 17 can't do that, you will have cold spots in areas, which will screw up your cooking. Unless you're a caveman and will eat anything anyway it's prepared.
Trust me on this. Get the 22 inch.