I build Archangel, but I can point 2 problems with it: 1) it takes ages to stack, so you still go oom in lane, because you sacrifice AP for tear, so the lack of AP means you need more q's to kill minions, hence you need to use more of your AA - thus it's more difficult to clear the waves; 2) it is a very slow build - you don't have damage in the first 15/20 minutes of the game. Syndra is not necessarily a late game champ, and relies a lot on her mid game. This is more of a late game build, and it does alrightish versus certain champsions, but if they have a pure late game champ, e.g. Anivia or Kassadin, she loses her mid-game advantage, and still isn't as strong in the late game as they are. Overall, unless you can get the jungler to gank mid in the right time, if they have late game champs, it's better to build Luden's.