Serger thread is polyester, thus, it has less lint than most cotton threads. It is also stronger than cotton threads. Matter of fact, I've found that it is actually stronger that cotton fabric. Why, you ask?
I have used it in my quilts for years, but recently I discovered that it may be TOO strong. I used it for the lap quilt EVERYBODY uses when they watch TV. First one in the room grabs it. I made it about 25 years ago, and the piecing stitches have finally started breaking the pieces apart. Same thing happened to a lap quilt I made for my DGS 12 years ago. Lots of love and it started coming apart.
So I guess that the folks who've been telling us to use cotton thread for piecing have a point. But 25 years of use for my quilt and 12 years of really hard loving for DGS's quilt is pretty good ... By the way, the rest of the cotton pieces were not worn at all - just the seams.