It shouldn't exist. Changelings haven't a chance. I'm not even sure how anyone would consider this a fair fight.
Daleks have destroyed entire species, the changelings failed on taking over Canterlot; The daleks win. also, this is my 100th post
OK, so the Daleks will kill everything forever BUT Who is a more engaging villain? Who's more interesting and more likely to keep your attention if you had never seen either before.
The Changelings have more potential interest, if only in a Invasion Of The Body Snatchers kind of way. Seriously, I never got why a species seemingly evolved specifically for infiltration made an open head on assault against a potentially stronger opponent. Major potential for a season 4 episode directly parodying Invasion Of The Body Snatchers. Most Dalek stories simply boil down to 'Evil-Tin-Cans-Gonna-Kill-Everything-(Again)'. And before you say it, yes I am aware of Dalek stories that aren't that, e.g. Asylum Of The Daleks. It is simply that most of them are.
Changelings are lame, sure they can change into colorful horses but they are look like them. Daleks try to kill all of reality, that is some epic stuff right there. Plus they've got time travel and space travel. Though none of it matters because the bad guys never really win in things like this.