If you want your writing to impact, be present. Past tense weakens the narrative and deadens the emotional connection with readers.
Present tense is a weapon, which use raises body counts. Over at the BetaNews, some commenters consistently accuse me of being an overly-emotional writer. I cock my head and laugh, because just the opposite is true. Ambivalence is my feeling about 95 percent of stories, if not more. But accusations persist that I am a killer. For sure—of past tense.