Majora's Mask all the way, it is a classic.
Majora's Mask is not all about the temples and killing the main guy. It is more about the side quests that get to me in this. Nintendo has done a fantastic job with the Zelda series in my opinion, they never let me down.
Very difficult. I didn't use help at all. It was so addictive though I barely slept. I beat the game in 1 week. The last day I stayed up till 7am to beat it. :3 Not staying up that late for a game again, I couldn't see xD.
MM has to be the best:
1. Harder story play(can't believe I beat it in a week though)
2. Get to play as multiple forms
3. A lot more side quests then OoT
4. You get to wear masks :P
5. This is just personal experience) try playing really late when your tired it makes the game play for intense...