Nunatak is a totally custom house. They list the default specs and prices for each item, but Tom will build just about whatever you want (within reason). You can choose either Pertex Quantum (2 different weights) or Epic fabric outer shells in assorted colors, the number, location, and removeability of straps, any dimensions you need (girths at shoulder, hip, and foot, overall length, overfill (including where it goes), differential cuts; you name it. That's what you're paying for. That also means longer lead times.
The only options I'm aware of with Katabatik are for overfill and a single fixed extra width on each quilt.
It's your money; spend it the way you want to.