Siding with the templars give some good things: some good soldiers (of course once disbandend the order
they can't even get that their boss is an envy deamon. really, great deamon/abomination hunters we have here... no surprise you let all mages run away...) Calpernia and the dwarven "radio". Barris...he survived in the run I sided with the templars, but I can't really see why people like him. Is bland and really forgettable. And is nowhere in Skyhold to talk to after. bah.
really don't make a change.
I really liked Cole's presentation, it was cool, just like it was cool the deamon. But there was nothing really new in the mission.
Siding with the mages was great on many levels: Connor, various point of view of the mages, Dorian, Fiona (I like her, can't understand where people see the mary sue, because she is flawed as hell, but I like her.) and the time magic. Is quite a big step in the DA lore, something that have never happened, quite more interesting than a more refined walk into the deamon territory. And the effect of the red lyrium on the various companions is heart wreking. Same as Leliana's condition in the future.
As I see it, siding with the templars is more good for new players. Less connections to the pasts games, more understanding of the basic lore of DA, while siding with the mages have lots of cameos and references to DAO and DA2. (Redcliff, Alistair/Anora, Fiona, Connor, Samson)