So I've finally decided to go ahead and earn the nightingale armour and from what I've seen it SUCKS if you want to just be a generic thief and that the thieves guild armour is so much better. My character is a generic thief who uses bows, daggers, all that good stuff so here are my reasons for why nightingale armour doesn't really make all that much sense.
Nightingale- Illusion spells cost 15% less to cast.
Thieves guild- Prices are 10% better
This one is pretty obvious. As a thief I don't use magic
Nightingale- Lockpicking is 20% easier. One-handed attacks do 20% more damage.
Thieves guild- Lockpicking is 15% easier.
The only piece of the nightingale that is actually useful and an upgrade
Nightingale- Wearer is muffled and moves silently.
Thieves guild- Pickpocket success is 15% better.
From what I've seen enemies have yet to show a different reaction to sneaking around in the nightingale boots, which makes them do pretty much bugger all especially if you have the Silence perk.
Nightingale- Increases your stamina by 30 points. Increases Frost Resistance by 30%
Thieves guild- Carrying capacity increased by 20 points
As a thief I don't expect myself to be needing any of those upgrades due to the fact that I'l be sneaking around using arrows and backstabbing to take people out. And the extra 20 points in carrying capacity is always worth it, especially if your like me and pick up every piece of crap you see
Remember this is strictly for traditional thieves and doesn't apply to people who like to mix and mach classes.
So what are your takes on the nightingale armour and sorry I'm EXTREMELY late on the subject. Haven't had much time to play the game ;)