I prefer 蠶絲被 than羽絨被.
If for people with respiratory problem, 羽絨被 is not suitable at all, even you got no such problem, the feature will come out after years, you will hate clear them up at your bed.
For cheaper choice 蠶絲+綿 is good.
I am using Cherry's 蠶絲+綿被 queen size (80"x90") is only about $600, I found it is good in quality and value for money.