From a tech perspective, and keeping in mind that I can presume the goal of human spaceflight to be to push humanity further into the cosmos, I see one thing really exciting about Dragon 2 that CST-100 doesn't have--propulsive landing. A NASA Ames research team says that Dragon 2 thrown by Falcon Heavy could execute a fully propulsive EDL on Mars. This seems like interesting heritage to build, and shows that development of Dragon 2 could have implications on further spaceflight.
Plain is good. Plain (in this context) is correlated with reliable.
Here's the thing with the STS. The lifting-body design spreads a critical system component (the reentry system) over a large area, necessarily on the outside of the craft.
A capsule with a more conventional ablative re-entry heat shield is more durable and reliable. It is also protected for most of the mission. It can be engineered with plenty of design margin (at minimal weight penalty), to deal with unexpected circumstances. That makes for a good design.
The TPS on the STS has partially failed several times [1], and once catastrophically.
It's much heavier than a Dragon v2, meaning it carries less payload for the same launch cost, for more or less the same land-where-you-want capability. It's pretty, but pretty does not solve the problem.
Perhaps Dream Chaser was ready to do all those things. I wish it went forward as well. But the technologies in Dragon 2 will make a big difference.
CST-100 makes similar promises if it can be matched with a reusable launcher (perhaps F9R). I'm not sure if they're looking at similarly short turnaround times (probably not). But they're much less far along and it's hard to judge if they can deliver.
Dream Chaser also makes similar promises, again if it can be matched with a reusable launcher. What's the advantage of it over the others? As far as I can see, the only real advantage is less gee loading during reentry. In exchange, you add a lot of complication and weight (wings and wheels). It doesn't seem worth it at all.
Spaceplanes look cool, but what's the point? The goal should be robustness and cheapness, with reusability a necessity for enabling the latter. Vertical powered landing with a capsule looks like an excellent way to achieve this.
They both look pretty plain to me. I mean, Musk can lay on some shiny metal here and there, but they're both soulless capsules. I really like the Dream Chaser; a 1/4th size STS that can be mounted on the tip of existing rockets is very tempting.
I think Boeing's marketing wants people to know that it won't have the Musk-like cult of personality, but it can deliver the goods, thus the talking points about hitting milestones.
I wish both of them the best of luck. This isn't a competition, its delivering LEO for NASA. I think people who see it as some kind of "my guy vs yours" are missing the point.