Learn English – Which tense should be used while comparing one dead and one living person using the word ‘both’

I think the rules can shift a bit depending on the style guide you're working from, but most would probably require:

• a comma before each quoted question
• a question beginning with a capital letter
• a question mark at the end of each quoted section
• no punctuation immediately following any of the closing quotation marks

Since the last rule would strip away both a comma and a period after the first quotation, the only way to draw a distinction between the example being one sentence or two is the capitalization of the word "[T/t]hey're," and each choice is grammatical. The main difference is the length of the mental pause placed when parsing the line, which may augment or diminish the rhetorical effect of the antithesis. The effect will vary from reader to reader, and many people may interpret them as being identical. Some people may also find one version easier to parse on the first attempt, but this again will vary from person to person (I personally find the two-sentence version easier to parse, but I see in the comments that Jim made the opposite observation).

Both are correct, there is not a need to insert a prepositional specifically because the word that the preposition would be associated with is a verb, if it were a noun or an adjective then it there be more president for a prepositional phrase.

To clarify, a Preposition does just what it sounds like, it pre-positions; quit especially in adjectives - in adjectives it is giving more of a spatial orientation, helping bring out the dimension in the adjective; simply put it makes it more 3D than 2D, so-to-speak.

Using a preposition in front of a noun, or pronoun is generally meant to specify or modify that noun.

You can see this in Shrunk & Whites book, you can also learn a great deal about it by looking at the etymology.

Personally, I find prepositional phrases useful in conversation - just as I would start a sentence with the word "And" if I were speaking but not if I were writing. Similarly, in writing I find they are often overused as are adverbs. When you get right down to it I believe it to be a matter of style, whichever you prefer is optimal. Hope that helps