No the Ariel is better than the NX2. The only thing it does worse is battery life. NX2 had all day and night battery life while the Ariel has about 2-3 hours of battery power when the sun is not shining.
In everything else the Ariel is superior.
I must respectfully but completely disagree with your assessment- the Ariel is a huge step back from the NX2. My NX2 went dead early this summer (the dreaded steady red status light). I contacted Solar and was told they are no longer servicing the NX2 or offering parts. So basically, I had no other option but to "upgrade" to the Ariel, which I did. From the moment it hit the water, it was obvious that the new robot was not ready for prime time. There was the obvious battery issue that others have mentioned- it stopped within an hour of sunset and wouldn't even run during the day unless there was full sun.
I also found that the new float design causes the front end to ride too low in the water, creating a significant forward wake. The result was that most debris ended up being pushed off to the side rather than sucked up. Placing a couple of hockey pucks on the back to lift the front helped a bit, but the pucks slide around and partially block the solar panels, so I would need to find a better rear weighting solution.
Lastly, I was really looking forward to the new proximity sensors as they would (hopefully) mean fewer stripped gears. However, the sensors prevent unit from riding the wall where most debris collects- something the NX2 did very well.
I finally got fed up and purchased a "repair or parts" NX2 on eBay. Got a nice deal since the gears were stripped, but it sounded like the electronics were good. Sure enough, I swapped the motors and had a working NX2 again. I then decided to find out if the NX2 really is better, so I placed them both in the pool and let them battle it out for 3 days. The results speak for themselves:
The only problem is that I know the gears on the NX2 will eventually strip, so I'm going to have to find an alternate source for replacements. As far as the Ariel, going to return the it and wait until they work out the kinks.