Which Akrapovic Exhaust?

[Treillw]

Hello. I have a 2009 KTM 990 Adventure and I would like to purchase a set of pipes for it. I was wondering if anybody could tell me the differences between the two styles of pipes Akrapovic has available for my bike - there seems to be two different pipes that would work, the Titanium Series and the Evolution Series. I haven't been able to find much information regarding the differences between the two. I'm looking answer the following questions: Which is lighter, are they both titanium, what is the sound difference between the two, and are they both street legal in the US? I would appreciate any information. Thanks.