Wolf. It's also got a good AR/weight ratio (for heavy armor) and mix/matches with a lot of Heavy armor (Like Dragon Priest Masks) better. Well, I mean the ones that work best for a Warrior, or Battlemage (Rahgot, Otar, Vokun, Nahkriin...)
In the light you mentioned, Linwe's set. I like the grey, and Enchantments better, plus it's sleeveless. You can also mix&match it with the TG/master set(and Nightengale Boots.) I don't like the Nightengale set. It's okay for a priest of Nocturnal/Nightblade, I kind of understand with the way She dresses, but as far as a thief/assassin, not what I would call inconspicuous. Really aught to be robes, considering what the Nightingales actually are. Linwe's set includes a lot of the same enchantments, only 35% bow damage instead of 20% off Illusion. It also looks a lot more like something a practical no nonsense thief would wear than a Nickel Plated/Blued Ninja.
[edit]I drove out to Kileen today, saw a brown neck in a dropped gloss black caddie with chrome piping, oversized alloys wrapped in rubber bands and dual fart cans. That's kind of how I see the Nightingale suit, for "western" rice boys who want the appearance of performance, without any idea how to actually get it...[/e]