I make him human every time. I tried the spirit path once and really didn't like it. He basically goes back to square one of where he was in Asunder, the ghost in the machine that manipulates people's memories and feelings then makes them forget him at his own convenience, regardless of the consequences or cost to the person he touched. I find something really disturbing in that level of manipulation, of borderline mind control, and specially in how much spirit!Cole relishes in having that much power over anyone. The sheer giddiness he shows in manipulating all those people at Val Royeaux made me side-eye him hard, it felt like he was this close to slipping from a spirit of compassion to a desire demon right there.
Human Cole hurts more and gets confused by things he doesn't understand and can't hide away from pain, his or others', but he knows it's all part of being real, and that even hurting is part of the process of learning to be real. He respects people's feelings more, he understands that some things are off limits, that maybe people don't want him snooping around in their minds and using their memories to manipulate their emotions. The two points that marked human!Cole as my go-to were first, him wondering how is he supposed to help people if they can see him (to which you can say, how about, you know, you just help them? - which somehow never occurred to him), and second, when he says he now understands why Cullen wants him to stay away from his memories. I got that last line way after I first got the line about Uldred from Cullen, so it really fit that now that Cole was human and understood what hurting feels like, he would have come to understand that he'd gone too far in his attempts to help Cullen, earnest as they were, and some things you just leave alone.