It may have been done on purpose, or perhaps just mere coincidence (although I would like to think the former is true), but while the contents of the two sagas are different, if you break them down into key components, you can find an awful lot of similarities. In both sagas:
- It starts as the crew enters a certain half of the grand line (Paradise and New World).
- The first Island is ruled by a group affiliated with the main antagonist (Baroque Works and CC and his goons).
- On that Island the crew takes along with them passenger(s) in need of their help (Vivi and Kinnemon + Momo).
- On that Island the crew also agree on their destination which is several islands away (Alabasta and Dressrosa and from there to Zou).
- On that Island the main antagonist becomes aware of the crew's opposition against him and begins pursuing it.
- A slightly weak point but still: During the saga the crew expands its forces (Chopper and the Heart Pirates along with who knows how many more crews).
- The main antagonist is a Shichibukai (Crocodile and Doffy).
- He seems to be a lot more powerful than Luffy and it isn't clear how Luffy can beat him.
- He is first introduced by an alias, but his identity is revealed shortly after ('boss'\Mr. 0 and Joker).
- At first the citizens of the country he rules, or desires to rule, think of him as their savior.
- Luffy needs to get to him several times before they can finally have the final battle (also fairly weak point, but still).
- Luffy and Smoker are captured and imprisoned together.
- Smoker ends up giving up on chasing Luffy and even aids the crew.
- Luffy is chased by a marine individual against whom he can't win (Smoker and Fujitora).
- He is blocked by Luffy's brother (Ace and Sabo).
- Zoro's opponent has an ability that prevents Zoro from harming him (Body of blades, and one that allows him to hide behind a mass of stone).
- The crew befriends the royal family which deserves to be in power (Nefertari and Riku families).
- At the climax of the saga the main antagonist instigates a civil war.
- It is still early to say anything but a crew member forms a special relationship with one of the enemy's crew members (Luffy and Mr. 2, and Franky and Senor Pink).
This is what I managed to think of for now. I'll post more if I think of anything, and I'm sure there will be more similarities as the current arc concludes.