As to water resistance issues related to acrylic? None. In fact in the store where I worked there was general agreement that acrylic is really a better choice for people who use their Rolex as tools versus jewelry.
Scratches to acrylic can be buffed out very easily where you will likely never get a scratch out of sapphire. Also, acrylic will survive an impact that will shatter sapphire. Further, when used on a diving watch, the acrylic crystal will actually compress into the watch under pressure - tightening the seal. A rigid and relatively brittle sapphire won't. Lastly, sapphire is usually heavier than acrylic - adding to the overall weight of the piece.
Rolex transitioned away from acrylic not because it was less functional - it was just a marketing choice. Rolex and other mechanical brands were under a lot of pressure at the time from quartz brands that were heavily pushing how thin their watches were. Remember Rolex "Oysterquartz"?. Oysterquartz was their way of trying to stay relevant. Sapphire was also just seen as more "modern" watch solution. Oysterquartz was eventually killed - but sapphire lived on.
Toward the end, gen shops were swapping out acrylic crystals for sapphire because those were the ones that would sell first - not the "old fashioned" domed ones. Part of that, I guess, was Rolex being discovered by the high end jewelry customer - not just the true sports watch (tool) customer. The jewelry customer cared more about it looking new and pretty than how it might stand up to a sharp impact underwater.