The performer is much sturdier to cart around the house. I store my kettle in the alley, but bbq in the yard. I always hated dragging the OTG through grass as the legs are kinda flmsy. I also don't really like the lid hook on the OTG. I used to hang it on the handle (It's alot easier than to hook on the bowl lip) and the handle would get dirty. The lid bale on the performer makes this a non-issue. The storage of the ss performer is also nice. The contents have never gotten wet, even though I store it outside uncovered. On top of that you have the table, baskets, starter, and ashcatcher.
On CL you can get a performer for less than the price of a new OTS. It's definately worth the upgrade or CL stalking.