I'll play Devil's Advocate here. I worked at a dive shop for many years and can tell you that no matter how loose fitting your wetsuit is, urine does not rinse out in the water. I've washed way too many rentals to know. Think about the smell of wet neoprene when you don't get a chance to wash your gear until the day after a dive. Wet neoprene itself doesn't stink. It's the body odors that have absorbed into the cells of the material. Soaking a suit in soapy water and sometimes having to scrub is the only way to remove the smell.
As to the old addage about the two types of divers, the only people who believe that are the ones who pee in their suits. Also, we're not talking about saturation diving here. Most people have no clue what dehydration is. If you are outside on a hot day and don't drink water, you will eventually begin to feel weak. If you're doing any strenuous activity such as running, backpacking or walking across the Sahara then you need to hydrate. If you can't spend an hour or so under water without peeing, you have too much liquid in your bladder. I always remind my fiancee to pee just before we dive so we don't have to abort in the middle.
One more note. If you are peeing to warm up, you will feel instant warmth, but you will soon be colder than if you hadn't peed. Try going a couple of hours without drinking before a dive and I'm sure you will find diving much more enjoyable.