Given enough horsepower in a machine, a very large buffer just isn't necessary. This was the point of introducing anti-buffer underrun features, so that small buffers could be used without fear of creating a coaster, thus cutting costs. Of course it is nice to have a large, comfy buffer, but it isn't necessary. While Yamaha's P-CAV does offer a bit of a speed improvement, it just isn't astounding. Burning an entire CD, the average speed of the Yamaha is less than 1X faster than the Lite-On. I agree that the Mt. Rainier has a lot of potential, but by the time it has enough support to be worthy, the drive itself will probably be around the Lite-On's current price, and DVD burners will be competing fiercely.
Certainly, I also agree that these features are beneficial nonetheless. I just don't see it as worth the added cost, but that is my opinion. It's obviously different from your's, so there's no point in arguing 🙂 What's important though is either of these drives will serve their user very well, and Arcenite will be happy regardless of which he chooses.