This is a tough one. I don't dislike the tomb raider-y levels in Thief Gold, but I think I do dislike the ratio. The opera house is the last actual thieving mission in the game, and it's a fair bit from the end. The actual undead missions themselves are kinda inconsistent, too. I absolutely love Down in the Bonehoard, but I'm really not a big fan of The Haunted Cathedral. Return to the Cathedral, on the other hand, is pretty solid, but I find that I have to be in the right mood for it.

Thief Gold also suffers from having its levels feel a bit too empty. Thieves Guild, Haunted Cathedral (first one), and Lost City all end up having fairly wide stretches where there isn't really anything interesting.

That being said, the story and atmosphere are, IMHO, far better than in Thief 2. It took me a while to realize how quiet T2 is! I miss those musical cues that would pop up from time to time in TG. I understand removing them because they can interfere with trying to listen for guards, but they just added so much to the atmosphere.

Thief Gold/Dark Project overall but I do think that Thief 2 has far better setting than the supernatural stuff in Thief 1 I do like the technological stuff in Thief 2. Some days I even think I like Deadly Shadows most lol.

Well I think TDP is more like an exploring/"thief" sometimes, the Designers sometimes did a really flawless work and sometimes not, 3 of the missions was like a maze and the the Opera house felt like "where I am" it was easy and was deep in the game.
I like the storyline, and its easyer (much) like the 2 in the human levels, but when the undead levels come to mind they are really a pain.
Some levels are a puzzle, and need to think atleast 2-3min what to do with your gear, I mean how to conserve ammunition vs the Undead always harder on these, while in thief 2 just bought water arrows and thats did the job. :V
The 2 its just so plain, and perfect feel like a professional thief not like an explorer in TDP/Gold, plus the rooftops levels gives some edge in gameplay/ Taffer have a great guide for 1-2 and says some helpful tips.