Best to know your audience, I guess. Analysis of two speeches, for what it's worth:
... Michelle Obama's 2012 speech to the DNC was written at seven grade levels above Ann Romney's as measured by the Flesch-Kincaid readability test.
The Flesch-Kincaid test is designed to assess the readability level of written text, with a formula that translates the score to a U.S. grade level. Longer sentences and sentences utilizing words with more syllables produce higher scores. Shorter sentences and sentences incorporating more monosyllabic words yield lower scores.
The First Lady's speech on Tuesday evening was delivered at a grade level of 12.84 - more than 3.5 grade levels above the next highest speech of the 10 previous prepared remarks delivered by wives of presidential nominees since the first such address in 1992 by Barbara Bush.
Ms. Obama also held the previous record with her 2008 speech with a grade level of 9.28.
At the very bottom of the list - some 7+ grade levels below the First Lady - is Ann Romney.
The wife of the 2012 Republican presidential nominee gave a speech written at just a 5.80 grade level last Tuesday evening at the RNC.