I use more 1.5 strips than 2.5 strips. I like the way the colors of smaller strips blend together better than 2.5. I have even cut jelly roll strips to 1.25 to get the better blending. I use the smaller strips in just about everything. Log cabin is a favorite , but pineapple , and just about any strip method quilt can be modified /reduced scale to a 1.5 strip or smaller.
I am not sure how many I would purchase .. since so many of the narrow strip method quilts I make are scrappy. I would be "in" if it was all tone on tone white on white or natural blenders , since I like the scrappy look for the "fill" strips in a scrappy.
So many books and patterns are geared toward the 2.5 width... and also fat 1/4s , one exception being log cabins.