To me, the Gun Metal looks better while the hard anodized stands up better to drops and wear.
The Gun Metal finish is still relatively scratch-resistant, but obviously not as much. I have carried mine in my pocket everyday for quite a while and there are no noticeable scratches. To be fair though, I have not dropped my Gun Metal E1 directly on cement.
The hard anodized finish is very scratch-resistant and will stand up to wear better, but it only comes in the OD green color.
So in summary, the GM finish is relatively scratch-resistant for everyday carry, but if you are using the light where it will be abused heavily and/or dropped occasionally, the hard anodized may be the better choice.
Bucky