What effect does shakespeare varying use of iambic pentameter have on the reader or viewer?

Compare how personal experiences are presented in the two poems

Which is it? the desert is than the mountains? 1. drier 2. more dry

Brutus: but as he was ambitious, i slew him. . who is here so base that would be a bondman? if any, speak, for him have i offended. who is here so rude that would not be a roman? if any, speak, for him have i offended. who is here so vile that will not love his country? if any, speak, for him have i offended. i pause for a reply. which rhetorical device does brutus use in this excerpt?