I'd have to say I
like both of them. I'm not sure which is 'better' though.
Each has some of the qualities needed to make an 'ideal' ship texture.
The 'plain' grey one does look like a more realistic color scheme for a spacecraft, but the dark grey/purple one is much more detailed and that gives it a 'real' feel as well. The lighting is better, too. Can you introduce more contrast into the grey one? The nose ought to darken on the side away from the light source just like it does on the second one.
If you could increase the lighting/shading effects on the grey one, and possibly add some more detail -- if the shading effect isn't what brings that out -- I think that would be best. Maybe if you convert the 'purple' parts of the second one to the same dark grey as the main body of the ship...