Anyone know or any real differences between boss sd-1/os-2 and od-3? Switch idea

[jimbob]

I was wondering this as from listening to them I dont suspect theres any real difference. Maybe same circuit different clipping ect?.. I just thought if so it might be nice to be able to switch between the few different types out there. Seems like a great idea to me.

Anyone?

Anyone know or any real differences between boss sd-1/os-2 and od-3?