[Usability] Zooming controls: slider or combobox?

[Debarshi Ray <debarshi ray gmail com>]

I was looking at the various "zooming controls" used in GNOME programs
to decide what to use in a program. Apart from the simple '+' and '-'
controls I found atleast two others -- F-Spot's slider, and
Evince/Epiphany's GtkComboBox. Is there a preference in favour of the
slider or the combobox?

Thanks,
Debarshi
-- 
One reason that life is complex is that it has a real part and an
imaginary part.
    -- Andrew Koenig