I own several and use them all for one thing or another. I have two old Kenmores and one new Kenmore, an old White, two old Singers (soon to be 3 I am hoping!) and also my MIL just gave me her old Viking Husquavarna. I have a few other machines that are in shapes from not working at all to just need a few parts... I guess you could say I collect them! LOL
But I use the ones that are working for different things... one of the old Kenmores is the one I use for machine quilting in the ditch, I use the newer Kenmore for most of my piecing but have used a couple of the others for this as well. I have an old Singer I am "training" to use for free motion quilting.
And my MIL's machine is the one I use for the blanket stitch applique as it has the best stitch for this!