Yes, a 15 class bobbin will hold more than a standard rotary bobbin, featherweight bobbin, 66 class bobbin. But I think a White Rotary will hold more, and a Bernina 7 Series machine will hold 75% more than the 15 class bobbin. M class bobbins hold about the same as a Bernina 7 Series bobbin. Don't have any charts with measurements, but I'm a sewing machine tech, and work with all kinds of bobbins.
Just a reminder...only use the bobbins that were intended for your machine.