On on some projects I prefer hand quilting because it gives me much more freedom. I use pearle cotton or any other thick (and very visible) thread for hand quilting. If I am going through the trouble of handquilting you better be able to see it from space
Also, when hand quilting I use many different stitches that look so much better when they are done by hand. Most can be accomplished with the new machines but they will make a piece look factory done. That being said, all of my quilts for every day use are machine quilted. There is an interesting book that I refer from time to time to that covers many interesting stitches. It is called The Quilter's Stitch Bible by Nikki Tinkler. It has about 200 stitches.