Difference between F&P 604 and 608?

I'm looking at getting the Fisher & Paykel HC604, but was curious about the HC608 and whether it's worth the extra $90? I don't have a problem making manual altitude adjustments, but is the leak compensation feature worthwhile? I'm at 8 cm pressure, using a swift nasal pillow, on the rare occasion during my month's trial with a HC234 I have awoken with the pillow slightly ajar off my nose and bothering me, but for the most part I'm fine and get a great sleep without the snoring. Any other advantages of the 608 over the 604?

I would think leak compensation is worth having. That slight "ajar" of nasal pillows (or any mask, for that matter) during the night can cause enough extra leak to warrant the machine needing to blow a little harder to maintain the set pressure. Without leak compensation, the pressure would not stay at the presumably therapeutic prescribed level.

Even though you wake up sometimes to be aware of the slightly displaced nasal pillows, you might be sleeping through most of the leaky times.

I've not used an F&P machine, so don't know about the pros/cons of any of the other features. But, I know I would want leak compensation built in, if it were me.