Lately neither of my machines do not like the Bottom Line thread - it has thrown off the tension something fierce. (One is Viking Topaz Sewing/Embroidery machine and the other is Janome MC6600P.) So now I use the same thread for both the top and the bobbin.

I had accumulated quite a bit of Coats and Clark over the years sewing that is still good but my machine doesn't like it very well - shreds and breaks - but works fine for the bobbin. I've been taking and filling bobbins with that and using it up. I have never seemed to have issues with getting a good 1/4" seam and everything fits together just fine so I go with it. Most any color will work for me since you don't see it anyway. When that thread gets used up I'll probably be more picky.

I like Connecting Threads Essential Pro Polyester. It's super fine (70 weight) and strong. I use it to quilt on my Gammill, too.

I use the same top and bottom, and none of my machines are fussy most of the time I use the Coats and Clark (I know, it is poor quality and turns out to be expensive) but I can get it in a lot of colors and not have a bunch of it sitting around when I am done. So that is my go to. I do have aurifil that I use for piecing sometimes. I have used sulky variegated for FMQ and that works okay.

Bottom Line by Superior in top & bobbin. I use it on my dsm & in the bobbin on my George sit-down quilting machine in the bobbin. Have never had any problems with either machine & I like the 60 wt because of the thinness of the seams. I use mostly neutrals for all my piecing but will match the top thread when quilting on George.

I use CT Pro for piecing and bobbin. I have a lot of Aurifil, Finishing Touch, Bottom Line, and Sew Fine I use. I like the Masterpiece pre wound bobbins too. I don't really care what brand as long as it's very good thread. I gave away all the C&C thread I had. It was older so the new version may be better. I know C&C cost more per spool for less yardage then the other brands. You are not getting a bargain.

I use the same thread in the top of the machine as I have in the bobbin-Aurifil. Love this thread.

Another Aurifil devotee here - I use 50 wt. top and bottom for piecing. Never disappointed!

Superior Threads Masterpiece, top and bottom. Strong, fine and pre-wound bobbins. Look for the sales.