Carl,
I have experience with the jacket that the Outdoor Gear Lab review said was the same warmth; the FF EOS. I also have experience of lab thermal testing most competitive jackets to the L3 Summit Hoodie.
Based on 800 fill providing the same warmth as the 900 fill EOS and TNF limited specs, we know the following:
L3 Summit Hoodie
Weight: 12.8 oz (M)
FP: 800
Iclo: 2.65 Iclo
TN Camp Chores: 31F
FF EOS
Weight: 10.6 oz (M)
FP: 900
Iclo: 2.65 Iclo
TN Camp Chores: 31F
Montbell Plasma 1000 Alpine Down Parka
Weight: 8.4 oz (M)
FP: 1000
Iclo: 2.59 Iclo
TN Camp Chores: 29F