I personally like warm and natural and/or warm and white, Hobbs 80/20 is also a good choice( it holds up the best if I want to preshrink for a flat quilt rather than crinckly look. I like a cotton because it is a natural fiber and is cooler in the summer.
If you do lean toward a poly look for bonded fibers , non- bonded is prone to bearding , thats when the poly fibers work thru to the front of the quilt and pill. This is especially important if there are dark colors in the body of the quilt top. Quilters Dream is probably the best choice for a poly.
SIlk is a wonderful choice if you want to hand quilt, but I do not think its worth the $$ if you are machine quilting. Silk bats are realitvely new to general availability so long term results are still unknown . Regular silk fibers are prone to dry rot .. so I would be reluctant. Silk is one of the most insulating fibers you can purchase ....ounce for ounce silk is warmer.