Well, the obvious difference is that one is inscribable and the other is not.
What this means in value terms is that the ones that are not inscribable are a lot rare, specially with max stats and low requirement. Where as the Inscribable ones will be dropping from the Zaishen Chest and presumably UW/FoW End Chests as these are the only sources of inscribable Tyrian Skins that I know of.
If the Serpent Axe also drops in Eye of the North areas then that will be inscribable and of course be a lot easier to come by than a non-inscribable variant.
There is no difference in the stats of the items, both are going to do the same damage and have the same apperance, just to some people (mainly collectors) pefer non-inscribable versions of weapons as they are lot rarer because not only do you have to find the perfect skin and requirement but the perfect mod as well. Where as with inscribables you could get a req9 max damage but with a rubbish inscription and just replace it for a 'perfect' weapon.
Someone else will probably provide a more consice description for you but essentially, yes non-inscribables that are of good stats are a lot rarer than an inscribable variety and therefore carry more value.