The Dolphin seems to be a more capable unit in some ways, and we both like the idea of a seperate bail out.
The seperate bailout is
needed on the Dolphin though, because the very high interstage pressure doesn't allow a normal 2nd stage to be plugged in to the 1st. And the bailout tanks are usually quite small and approach the limits when diving around 40m.
In both my and my wife's opinion the Ray breathes better in all attitudes in the water. But it is more uncomfortable to dive, e.g. laying on your back and looking up.
That of course is due to the position of the counterlungs over the shoulder on the Ray. The Dolphin, like any RB with backmounted CLs, has a sweet spot where it breathes well. In any other position the WOB will be higher, even uncomfortable. You'll also produce more CO2 during labored breathing.
Another downside of the Ray's fixed CLs and one size doesn't quite fit all harness is that it simply doesn't fit every diver.
The Dolphin's single dosage device is nice; the various orifices are different units for the Ray.
That means two things: The Dolphin is more versatile, if you know which depth you'll be diving there's a good chance that you'll get a better match from the orifice/mix.
And the Ray's complete replacement dosing and bypass unit cost considerably more than the Dolphin's 32% orifice (the 40, 50 and 60%s are standard), thus making up some of thr price advantage.
Finally, there are considerably more aftermarket bits and pieces for the Dolphin than the Ray. If you want to balance the unit and add larger tanks to the side, you can add a ss subframe backplate, for example. Mods like this will mean cutting up the Ray.
If you need less scrubber duration you can use Dräger's spacer to reduce the amount of Sorb you carry and thus the duration.
Between the two, I like the Dolhin considerably better. Then again, the Ray barely fits on me in the store, so I didn't bother trying it with a drysuit.