Hexigo has a lot of things figured out. It looks clean, and modern, and allows people to contribute to making a decision. However, it does fall short in many ways as well. First (and most importantly), it is closed source. This is a complete deal breaker. Watching the demo video it also sounds like the final decision is ultimately made by a "group administrator", which almost defeats the purpose of making a decision as a group. The interface itself seems to be a pretty standard forum with sequential posts, and voting amounts to a simple yes/no.
Overall this platform is far more impressive then other platforms, but doesn't push any boundaries.
D-Sight looks like it falls into a similar category (closed source). The platform sounds like it is more focused on analytics than transparency. The demo video shows a lot fewer details about the platform itself, but the screenshots are mostly focused on graphs.
Contextoo is very slick. The interface is really nice, and it actually lets you create a new "board" without an elaborate signup flow. The platform itself seems to be geared at more trivial decisions. Instead of a problem statement you add options that users can vote on. Comments can be added, but are only sequential and appear in a side panel. Despite the nice design it feels like a voting app with a twitter feed on the side. All that aside, it is closed source, so not really viable.
From the slides at the bottom of the page, Review19 sounds right on point. The idea of bringing diverse opinions onto a single platform and drive decisions from facts and analysis. The platform still looks incomplete, so it's hard to judge the interface itself. It does not appear to be open source.
Overall the closed source platforms had cleaner interfaces and better visual design. I was still surprised that no one was really pushing the boundaries on interface design. Most platforms still looked like a typical forum or message board. Opinions were expressed in a binary yes/no, instead of providing a wider array of possible options.