With Option A, the logo is consistent and stands out which I think is more important than the background.  With Option B, the background is always the same and the logo color varies depending on your buckram color (although I guess you could make that consistent by choosing the same buckram color for all your Vertigo books).

1.5" is a nice size although I've had a few Vertigo binds that are smaller than that.  But it depends on what you mostly have planned.