It is a matter of personal taste. Keep in mind that this group on this site is largely self selected and prefers the more angular styling of the Sky.
Along the same lines, Anne Asensio, Executive Director of Advanced Design for GM, also notes that Cadillac has been quite successful with the bold angular styling.
Now, having said that, don't forget that the entire reason that we have the Kappa platform at all is that the reception of the Solstice at the 2002 International Auto show was so overwhelming that Bob Lutz felt they had to put it in production. The original Sky concept (which looked more like an Audi TT) didn't attract enough attention. The Sky was introduced in its current form as a production concept in January of 2005. There was some press, but nothing like that of the Solstice 3 years earlier.
There have been other concept cars based on the Kappa platform, including the Saturn Curve, the Chevy Nomad, and the Vauxhal Lightning.
It is a matter of taste, and arguing about which is better is interesting, but will never be a winnable argument. It will be the demand and the production numbers that determine how many of each are on the road.
As brentil said, it's a halo car designed to attract attention to the brands, and GM really knocked it out of the park because both models sold out with very long waiting lists.
In point of fact, the waiting lists at the Pontiac dealerships were pretty much the same size as those for the Sky dealerships (mostly between 8 and 20--even for smaller dealerships), so just comparing the numbers, with 480 Saturn dealerships versus 2800 Pontiac dealerships, the numbers do have something to say.
Of course, there's a self limiting effect, much beyond 20, most people will give up and decide it's too hard to get one, so the upper bound for the total number of people on the waiting list is about what you would expect.
One final thought: this is the first time that any manufacturer has made their halo car an affordable car. That in itself is a new concept. It has clearly worked, and these cars will be very popular for a long time to come.