I love down coats so over the years I've bought coats from Burberry, Herno, Canada Goose, Moncler, and Woolrich, as well as a few less expensive brands like Theory, North Face, Patagonia, etc. If you're looking for a fashion-forward coat, I'd go for Moncler or Herno. I find they are cut and tailored super well, especially for the more feminine styles, and also warm plus light. I wore a Burberry down coat for years because I thought it was stylish but it just wasn't as technologically advanced as the dedicated winter clothing makers so their coats were super heavy. Moncler and especially Herno do go on sale so I'd keep an eye out for those; I personally find them too expensive full price, for a coat you might not wear year-round. Mackage is an alternative that's really popular as well - it's Canadian-based and Meghan Markle is a fan of their coats.
If you're looking for a coat that can serve fashion and more rugged use as well, like a hike or skiing, I'd go for more heavy duty coats from Canada Goose or Woolrich. I prefer the latter - their fabric is less prone to fading and wear than Canada Goose and the brand is more low key. They do tend to be made for much colder weather than Monclers and Hernos though so you may not get as much use if you run hot often or don't live in a super cold climate.
