Jeez things moved fast while I was trying to reply.
To me though Solas is extremely selfish. During that companion quest he really is only out there for what he feels what a Spirit should be. He isn't really there for what Cole really wants.
Because talking with Cole and understanding him, I always assumed that Varric is correct during that quest. Simply the way Cole speaks about himself.
I feel like Solas completely ignores this fact because Cole IS a spirit.
Solas always seem so kind of a selfish character. The more I got to know him and going through multiple playthroughs I see him as more selfish than selfless and more confusing and strange than he was wise and involved.
Solas is a serious fish out of water. He's very much displaced in the current Thedas, which is why he's probably coming off as confusing and strange to you.
Varric is wrong. Cole tells you in the very next scene in his companion quest that he came through the Veil to help the human Cole, not so that he could become more human. Cole may well be a very unique case - most spirits encouraged to do what Cole did probably would have become demons.
Taking the spirit path has Cole thanking the Inquisitor for accepting him and believing in him. He's happy both ways.
No one in Cole's companion quest takes ten seconds to ask Cole what Cole wants. Not Solas and not Varric and not the Inquisitor.
It is an interesting issue, one I usually agonize over. I tend to like Cole as more persony (sorry I'm a sucker for the "become a real boy!" trope and also, come on, who's not curious to see if a spirit can become real?), so I actually defy My Precious and side with Varric, ultimately. Cole seems to like becoming more human, as you can talk to him after and he expresses his happiness. I'm sure he's happy the other way too, because that's usually how BW rolls.
I also like how, if you side with Varric, there's some banter later where Solas basically notes on Cole's changes and is impressed/intrigued, and I'm just like *see* 
There *is* one option where your Inquisitor can say "As long as it's what Cole wants" but it's not like he ever responds to that, so yea it is up in the air -- I think BW did that so people won't feel obligated to side one way or the other.
Editing for typos! So many.