"Each X" vs. "each of the Xs"

Are each X and each of the Xs interchangeable?

For example, in the following sentence, I would use each of the characters:

Each of the main characters is interesting.

But one could also write the following:

Each main character is interesting.

Instinctively, I prefer the former. Am I right, and if so, is there a written rule favouring the former sentence?

For what it's worth, Google returns 724,000 entries for each main character, and 11,600,000 results for each of the main characters.

Both are correct. In the first example, each is a pronoun, and in the second, it is an adjective. It is properly used in both cases, and meaning-wise, the two usages are interchangeable in my experience.

As to how common each usage is, I graphed Each character vs. Each of the characters on Ngrams, and Each character appears to be preferred:

http://ngrams.googlelabs.com/chart?content=Each+character%2CEach+of+the+characters&year_start=1800&year_end=2000&corpus=0&smoothing=3

However, googling the same thing yields opposite results (131m to 7.26m), so I would tend to conclude merely that both are common. Definitely both are understood, so the use of either should never prove a communication impediment.

To directly answer your last question, no, there is no written authoritative rule favoring either. You may be able to track down subtle nuances between them, but even in that case, both are equally valid within their respective domains.

'Each main character is interesting' seems to place the emphasis on the play as a whole, much in the way that 'All the main characters are interesting' does. 'Each of the main characters is interesting', on the other hand, stresses their individuality.

I find it quite annoying that your "instinctive preference" in favor of "Each of the characters" over "Each character" apparently is borne out by google statistics, since my own preference is opposite that.

Be that as it may, the same pattern occurs for some other nouns or pronouns after each, as shown in search-result examples below. I never imagined, before doing these searches, that "each of the ones" could possibly occur more often than "each one". You will note that most of the examples follow the pattern where the "each of the x" form is far more common than the "each x" form. However, I'm proud to say I found an example that not only reverses the pattern, but does so with a ratio of 234 : 1!

• "each name" ... 2,080,000 results
• "each of the names" ... 240,000,000 results
• "each one" ... 85,500,000 results
• "each of the ones" ... 170,000,000 results
• "each hat" ... 274,000 results
• "each of the hats" ... 1,350,000 results
• "each moment" ... 3,900,000 results
• "each of the moments" ... 11,800,000 results
• "each wombat" ... 943 results
• "each of the wombats" ... 4 results