Trailblazer or Viper
I believe the general consensus is viper is better, but if you need the survivabilty the choice is yours.
Depends on content.
For WvW and/or open world – Trailblazer might be better.
For group content like fractals and especially raids – every defensive stat is a negative point for the party (Viper is a clear choice). The longer your target lives the more damage all of you take. Toughness is not going to negate this difference.
“Observe, learn and counter.”