"Which model is right for me?"
The Stainless model offers the most versatility. It can be used with just about any clay type as long as the clay is soft and easy to work with your hands. Because stainless steel won't rust, it is ideal for use with white stoneware clays and porcelain. If you're going to be using these clay types, then the Stainless extruder might be your best choice. The Stainless model is offer as a stand-alone unit, without dies, or in value-priced packages.
The interior of the Standard extruder is plain steel. If the barrel's isn't washed out and periodically protected with a light film of machine oil or silicone lubricant, then it can rust or develop light oxidation that can stain your clay. Keep it clean and dry between uses and the Standard model can be used just like the Stainless model. The Standard model comes with the Basic Die Kit and one blank die installed.
In these extruders, the handle length and barrel size are matched to give plenty of leverage without ratcheting. There are no dangerous shackles, fewer pinch points, no clumsy multi-jointed handle to come loose, and no post or ratchet parts to wear out. The handle is anchored at one fixed pivot point, completely eliminating the danger of a heavy steel bar slipping or suddenly offering no resistance. Clay is loaded with the handle in the down position, again eliminating danger from a heavy, hard-to-control handle.
Finally there is this simple but very important note: These machines hold about eight pounds of clay, which will give a longer extrusion than most people can handle at one time.
Every extruder comes with 8 coil dies, 2 handle dies, one square coil, one hex coil, a blank die and a die mask. Several of the coil dies contain 4 cavities of different sizes and the die mask is used to block off any three of them. The Accessory Die Kit, which may be purchased separately, contains a stainless steel Z-Bracket (die brace), 4 coil dies, 2 ribbon dies and 6 hollow dies.
All dies are made of 1/2 inch thick polyethylene, which is extremely wear-resistant and completely non-contaminating. The top edge of the die cavity is beveled to compact the clay as it passes through, giving a crisp, more solid extrusion. In the hollow dies, there is a bevel on both the interior and exterior portions under each side of the bracket (which holds the center of the hollow dies) that helps the extrusion to "heal" after is has been cut apart by the bracket. This bracket fits into a Z-shaped slot machined into the top of the hollow die and is held in place by the barrel of the extruder. If a hollow die is mounted in place, the center part of the die is in exactly the right place and the wall thickness will automatically be even all the way around.
Note that in the stainless extruder, everything that comes in contact with the clay is either stainless steel or plastic and will not discolor the most delicate porcelain even if clay is left in the machine.