Each has certain advantages and disadvantages, and since I have used both kinds, each for a long time, here are my thoughts.
The plastic one is light and easy to move around. It is also cheaper, so if you aren't sure if you will stick to growing wheatgrass, you can use this kind at first to try it out. The disadvantages of the plastic kind are that they aren't as durable, and won't last as long. I started out with the Healthy Juicer, a plastic one, and it worked fine for me. That said, I now use a stainless steel manual juicer and it is definately better.
Here are the advantages of using a stainless steel juicer like this one.
- It is virtually indestructible, and will last a long, long time. I don't think I could break mine if I tried. I expect it to be around long after I am around! This makes the price worth it. It will however break your other dishes if you accidentally drop it in the sink!
- It extracts the juice better than the plastic kind. I can put the pulp in 2 or 3 times to make sure I get most of the juice out. With the plastic kind, it gets stuck if you try to put the pulp in a second time. The amount of extra juice you can squeeze out with the metal juicer is quite a bit--about 20%-30% more. If you get 15 ounces out of a tray, this will give you 4 extra ounces--Sweet!
- Stainless steel won't rust, and it stays very clean.
- It builds up your amr muscles, since it takes some effort to crank it around. (If you can't crank it around, consider an electric wheatgrass juicer)
In my opinion, the stainless steel juicer wins hands-down. Happy Juicing!