I have never cared for the use of insulated clothing as an addition to a sleeping bag not sufficiently warm enough for the ambient conditons, with the exception of either my Richard Egge "double duvet" down parka or my I.D. Dolomitti parka plus an "elephant's foot", my latest one is from "Wildthings" and is Epic over Pl.
Many will hotly argue and likely condemn my choices, possibly even deciding that they are not within the purview of this forum, but, I have used a lot of down jackets and several synthetics in western and northern Canada for 45+ years and find little difference between them. The DOWN is FAR superior in real cold, 0*F and colder while I like my Montbell Thermawrap Ultralite for summer use, my I.D. Rundle jacket ( I have two as a result of a gift from my wife when I had already bought one....hard to take, but....) for hunting and BC coastal use and the I.D. Dolomitti for interior winter trips.
When it is -20*F and one is out for several nights, a really good down parka and the old EGGE was the finest in it's day and still better than most I see available as only PHD in "merrye Englande" makes down parkas of that quality nowadays, is THE way to go. I have never had this wet enough to have problems and have even carried a full expedition-sized pack while wearing it and using X-country skis to come 11 miles out to the highway from a camp I used to keep all winter in the mountains near my hometown.
Today, with the price of down gear, I would tend toward Primaloft and I.D., Wildthings or Montbell as sources. The discrepancy in weight in the M.E.C. gear is pretty typical of their stuff, IME, but, "you get what you pay for".