i use my 1972 830 bernina for just about everything, but my 1960s Elna Super is great for doing paper piecing and HST/Flying geese. That in itself is enough reason for keeping two machines. Now the other 6 I have no good excuse for but they need repair and tuning anyway.
Oh yeah, they keep my studio from blowing away in the wind, yeah that's it, keeps the studio on the ground.
tim in windy san jose