From hardest to easiest.
1. Eldin Volcano.
2. Lanayru Desert.
3. Faron Woods.
4. Skyloft.
Eldin Volcano was hardest because i wasn't familiar with the area very much, i had never really explored it. Also, i forgot about the two geisers that blow you to the middle, on the slide thing, so it took me about 10 tries for the Eldin Volcano silent realm.
Skyloft silent realm was definately easiest because i was so familiar with the area, and i new how to get everywhere, and pretty much where everything was. Also, the tears weren't very hard to reach. I beat this level first time, in about five minutes.