Dragon Age: Inquisition's companions each have their own personal quest. Cole's is particularly interesting, as it involves Solas and Varric as well as the Inquisitor. It also involves making a choice that will affect Cole forever. Players get to choose whether he becomes more spirit or human, which determines his abilities and personality from there on out.
Like with all Dragon Age choices, there is no wrong answer to Cole's quest. Fans have had a pretty even split between those that make him more spirit and those that make him more human. There are a lot of pros and cons to either choice. It also makes fans wonder if it will have any effect on Dragon Age: Dreadwolf.
Cole As More Human
Choosing to make Cole more human is what Varric wants. This option makes Cole more complex. He does not throw away negative feelings, but rather sits with them and accepts them. On the pros side, he is more capable of complex thinking. He finds he can heal pain in ways he never considered before now that he understands how complicated people can be. As a human, he is also able to remember the original Cole and all that he learns in life. The cons to this choice are that Cole loses a lot of his spirit abilities. He struggles in making people forget about him. He also keeps the trauma involved in being human, which is trauma that was not originally his as a spirit.
Cole being more human is a very Varric-centered choice. Varric's ideologies are very much about defying one's roots. Just because he is a dwarf does not mean he lives underground and feels connected to the Stone, and he thinks Cole can be the same way but in terms of his roots as a spirit. Varric sees the world much like a writer does, that people should be shaped by their environment and experiences. Making Cole more human does exactly that. It's possible that Cole will appear in Dragon Age: Dreadwolf, and if so, being human could give him a deeper understanding of Solas' issues.
Cole As More Spirit
Choosing to make Cole more spirit is what Solas wants. This option makes Cole go back to his original form as a spirit of compassion. The human world no longer affects him so much, and he is able to use his powers to a greater extent. He can make others forget things, not see him, and even return to the Fade after the events of Trespasser. On the pros side, a lot of fans see this option as releasing Cole from trauma that was never his in the first place. On the sober end of this choice, Cole can make himself forget things, so he can forget about the original Cole as well as whatever else he finds uncomfortable. He cannot grow and while he has more power, he understands people a little less when their thoughts are complex.
Like with Cole being human with Varric, the spirit choice is very aligned with Solas' way of thinking. Solas' ideology is opposed to Varric's, and is very much based on stagnation rather than change. Solas does not value change as Varric does. Solas woke up in a different world, one that he deems has changed for the worse. Cole becoming human is another example of that. Solas struggles with change and finds that sticking to one's destiny is more comfortable and natural. Cole was originally a full spirit, and thus will be happier that way. If Cole appears in Dragon Age: Dreadwolf as a full spirit, it is possible he could be of great help to others through his powers.
Dragon Age: Dreadwolf is in development.