I own the MH Chugah pants. I don't own the ID Denali Pants so I can't do an authoritative side by side comparison on the weights, and loft but I'll evaluate what I can...
I use the Chugach pants for winter climbing (not backpacking or snowshoeing) so they need to have some features and be durable. The Chugachs are full of of features. Fully separating side zippers so they can be put on without having to take off boots, skis or crampons. Reinforced fabric knees and seat, two zippered fleece lined side pockets (a feature the ID pants lack), elastic and Velcro adjustment on both waist and ankle hems. The also have a nice articulation to the knees. Finally they have a zippered fly that you can belay through.
The Chugachs are comparable in weight to the ID pants. My medium Chugachs weigh 20 oz and the listed weight for the ID pants is 19 oz. Since I don’t own both I can’t do a side by side loft/weight comparison.
I measure the Chugach’s loft at about 0.8 to 0.9 inches, single layer. This is similar to ID’s reported loft 0.8 in for 4 oz Primaloft on the Denalis. The Chugahs are quilted about every 4 to 5 inches to the shell fabric which will reduce their warmth and loft over un-quilted PG. The Denali pants are un-quilted so you will get the full loft of the Primaloft Sport Insulation. ID uses the Sport over the PL1 because it is more durable and stable and doesn’t require the quilting that PL1 does.
One definite advantage for the Chugah pants are the seat and knee reinforcements that the Denali pants lack. Integral addresses this somewhat by using a 40 denier fabric that gives the pants some overall durability and improves the life of their DWR finish. Neither pants have a reinforced kick panel on the inside of the ankle. If using the pants in active per suits, unless you put gaiters over the pants this area is very prone to damage in climbing and other abusive activities.
I do agree that Polarguard has the edge over Primaloft for insulation but this is only one piece of the whole product performance issue. Quilting, how the garment is constructed and what features it has all play a role in the total performance of the garment. For instance a lightly or non-quilted Primaloft garment may well outperform a heavily quilted Polarguard garment.
BTW the new ID PLQ Pants weigh 10.0 oz and have .63 inches of loft. Not as durable or as featured as the Denali pants but almost as warm at ½ the weight.
Hope this helps,