Welcome, Greg, from California.
For piecing, I LOVE Aurifil 50 wt cotton. For machine quilting (with my 15" Bailey) I use essential pro 3ply 70 wt polyester from Connecting Threads. I recently quilted a small piece (on my Singer 15-91) using size 70 bobbin thread and this thread became almost invisible, allowing the quilting itself to shine. I decided to give the bobbin thread a try after it was recommended by Karen McTavish in a class I took at the Machine Quilters Expo in Portland recently.
I've seen a lot of negativity about Coats-N-Clark thread lately, but I really haven't had a problem with it. A lot will depend on your machine. Some machines like some threads better than others. My vintage machines seem to handle just about any thread, with the exception of nylon invisible thread.