I’m not familiar with Butler Bags, but I’ve owned several bags/quilts for camping and backpacking. It depends on how you plan to use the bag and your expectations. Butler’s all season bag, at $525, weighs 22 lbs. That’s pretty hefty, considering my 10 degree down quilt weighs less than 2 lbs (and cost $150 less). Pound for pound, good quality down beats any synthetic fill for warmth. My quilt and sleeping bags each pack down to the size of a football. Sorry fellas - size matters!
In reading the Butler Bags website, these seem popular for cold weather hunting and fishing locations. Another company to consider is Woods Canada. They have some nice stuff and the prices are more reasonable.