Good questions.
"First, and especially as a chemical engineer, how ca you recommend the use of EG in a marina sanitation system? I would venture that less than 1 percent of boat owners would even consider collecting the discharge from their winterized holding tank. That would mean the EG would be discharged into the environment. EG is highly toxic and that is just irresponsible. So PG is the responsible chemical to use for winterization. Not sure how you could recommend anything else."
I am sure of these facts. EG is no more harmful to the marine environment than PG and the US EPA agrees with me. While EG is toxic to mammals (do NOT use EG in potable water systems) it is not appreciably toxic to marine organisms and no different than PG. Those are plain and irrefutable facts backed by the links below (and more). Different biology, just like feeding chocolate to a dog is bad or zinc is good for humans. EG is safe as safe in the water as PG. However, I would hope that the first pump-out would be into a POTW, which renders the point mute, since both are readily treated.
http://water.epa.gov/scitech/wastetech/guide/airport/upload/2005_10_07_guide_airport_airport.pdf
http://www.sciencelab.com/msds.php?msdsId=9927167
http://www.sciencelab.com/msds.php?msdsId=9927239
"Second, urine is only a factor if you don't flush with water after use. Your joker valve should not be sitting in urine."
Very true, you are correct. But some folks don't flush enough. I have seen urine-stiffened valves in the process of researching. Yuck.
"I have been using the ratarian joker valve for over 2 years without a problem. The pump is plenty strong and we have not had any issues with additional clogging. It closes better and that is what prevents the back flowing."
True enough. We have tested both and reported no problems with either. Some of the test boats preferred the easier pumping, but you should observe that all three valves were, in fact, recommended.
"I think the PS article was good but I generally don't just pay attention to the conclusions. I read the test methodologies and results then draw my own conclusions. "
I think that is a healthy attitude. The data is the data, but interpretation is often foggy or individual. I think the most important part of the article was to warn sailors that PG in Jabsco heads is a poor combination; either EG or drain dry.