I usully use connecting thread 100% cotton thread for piecing and FMQ. My machine likes it , price is good, and it come in many colors. I have tried C&C 100% cotton and do not like it. It seems thick and linty so I do not use it. I do however use C&C duel duty for my general sewing. It can be bought cheap with coupin at Joanns. I will also use it ocassionally for FMQ if I need a special color.
I recently heard a quilt shop owner say that Acufill is her thread of choice. It is expensive but you get a lot on the spool.