I used basic Dual Duty and mostly white at that for decades. When they started making multiple types with multiple colored spools was about the same time I was switching to so fine.
Back in the day, the quilt police didn't like Dual Duty because it is a cotton wrapped poly thread and they were concerned the poly would cut the cotton fabric threads over time. I can tell from long experience that it never cut through my seams, nor did it impact the quilted fabric. A lot of modern quilting knowledge came from quilters of the 20s-30s and was based on valid concerns of the day but maybe aren't so valid any more. Especially in terms of poly threads, they are not what they were in the 70s and can take my hot iron just fine, feel nice, aren't brittle...