Tough choice. I owned and used a CS Amerique for over 4 years. Great smoker. A controller that was very simple to use. No 'programming' required. The racks are nickel plated, not stainless steel, and compared to the SI 3D, small. But they are adequate and the smoker will serve you well. By your description, it is out of warranty. One word of caution: IF the controller dies, it will cost you more than $700.00 for a new controller unless CS is feeling generous. Made in USA.
I now own the SI Model 3D. It is deep enough to swallow entire whole packer briskets; no folding or cutting. Racks of ribs lay the full length of the racks. The controller, not as simple as that on the CS is of the PID variety and very accurate. It only took a couple of cooks before I had it mastered and setting it only took a minute of my time. The racks are heavy stainless steel. Wheels are larger and you get a longer power cord (12 feet). It has built in handles to assist in moving it around. The heating element is a higher wattage. And it is new so you get a full new warranty. Imported.
Given the choice of used versus new, I strongly recommend new; get the SI. Get the best warranty and customer service in the industry. The choice is yours. Both are of the highest quality but I have to be honest and say dollar for dollar the SI is the better value. Good luck.