Greetings Liz,
I'm familiar with several of these devices which you reference in your question.
Moreover, members of the Walnut Council may be able to recommend certain devices over others. The National Walnut Council website is http://www.walnutcouncil.org/
Feel free to look at the state sites and the state representatives and contact them directly for feedback on the "best" nut crackers they've experienced.
To peak your curiosity, you may wish to look at the following websites:
http://www.redhillgeneralstore.com/A52207.htm
http://www.nutgrowers.org/QA/nutcrackers.htm
Best of luck!