Ptarmigan will be warmer, heavier and won't pack down as small if that's a factor.
I sold my Ptarmigan when they had advertised specs of 5 oz down fill.
Went to the Ghar because I don’t use hoods often and felt like I was cold more than I wanted to be in the Ptarmigan.
Ghar has 5 oz down fill plus synthetic fill in the armpits, top of shoulders and sleeve cuffs so it has more insulation than the Ptarmigan by a good amount and my use agrees.
Still have the Ghar after 3-4 seasons and don’t regret my choice.
Now SKRE varies the down fill with size so only way to find out is to call them.
The Ghar is definitely less roomy. I have a small size one and I’m 5’6, 156 lbs and can only fit a baselayer and the outdoor vitals Ventus hoodie underneath the Ghar.I’m the same size in both with a similar fit. Ghar might be slightly less roomy going from memory