Montane Extreme is a pile and pertex coat designed to keep you warm whilst moving/working in crappy damp winter conditions. It’s a great coat for its intended use but it is not an insulating garment so if you stop you will get cold fairly quickly.
Primaloft is the market leader in synthetic insulation but there are other alternatives that are just as good
Google clo-rating, synthetic insulation comparison etc.
Also beware the different weights of each material, e.g. Primaloft Sport 60g/sq m vs 133g/sq m so that you compare apples with apples.
If you want something cheap, simple design, tough and very warm then the Keela Belay is great