I agree with the suggestions for a 100% natural fiber - be it cotton; wool; silk. Those fibers breathe and keep you warmer when you need it to and cooler when you don't. As someone else mentioned, check the package labels for quilting distances - that might be your determining factor. Since you're planning to do in the ditch quilting, if your blocks are large you might need to go with something like Warm & Natural (or white) which only requires quilting every 8-10 inches. If your blocks are smaller you might be able to use a different brand.