I thought the topic was going to be about plastic or metal bobbins.
I learned how to sew with the vertical bobbins, so I'm more comfortable with them. I was totally at a loss at how to thread a drop-in bobbin machine because it was different! (It can't be too difficult - my (sometimes) air-head son can manage the Singer 404!)
I can purchase plastic and/or metal bobbins for three of the machines I have now. They seem to behave equally well with either - even though the people at the Creative Sewing shop said I should use whatever the tech had put in the machine when it was cleaned, oiled, and adjusted.
Singer Fashionmate 237 (probably late 1950s or early 1960s)
Singer 404
Pfaff Creative 1471 (I think) (late 1980s)
The Necchi BU only has metal bobbins
It would be helpful if bobbins had some sort of identification on them - such as 15 or 66 or SOMETHING!