Only on European guns do U usually see the serial # on the barrel, slide and frame. In America, it is only required on the frame. So, covering that is no issue. On American brands, U'll only find the #'s on the frame anyway. My SW99 only has it on the frame.
It is my understanding that in Europe, the barrel is more the firearm, instead of the frame.
As for the Titanium finish - I think the hard chrome is much more durable, and looks the same. Plus, you don't have to have "Titanium Finish" written on the side in text when you have it hardchromed