Hi Willy,
I prefer the goggle type because they fit over the top of my ordinary spectacles. Mine came from Lumenis and are primarily intended for YAG 1064 nm but are still rated OD 5 at 10600 nm - but as Bart has said almost anything will do for the CO2 wavelength.
One point, which I think was mentioned elsewhere, is that these goggles give no protection against the bright visible spot produced on the surface of the work. Unless you wear welders goggles you are likely to get 'arc-eye' from staring at the spot too long.

Tweakie.