When I last replaced my spicer u-joints I consulted a local specialty driveline shop. I wound up selecting the non-greaseable joints you mentioned. When I questioned their durability I was told they are often used in severe duty agricultural water pump applications, where pumps are continually outdoors or only sheltered by a crude cover. The rubber seals on that style are stiffer by design to prevent grease from being flung out during rotation. I was assured that they would hold up for many, many years in a car that is only occasionally driven.
A side benefit is you will not need to clean up far-flung grease after your annual lubrication routine.
Larry
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