Do you want it to be a truthful account of who you were? Or do you want it to gloss over your warts and tuck a little here and there?
Perhaps you've sat at a funeral and heard the eulogy and thought, "wow, why can't I be as good?"
The eulogy is a memorial. The obituary is a news story.
On the Washington Post's Post Mortem blog (yep, it's written by the obituary writers), Joe Holley kicks around this question of truth vs. memorial, and provides some decoding of the language, at least so far as the London Telegraph.
"Convivial," for example, meant the deceased was habitually drunk. "A powerful negotiator" was his description for a bully. "An uncompromisingly direct ladies' man" was Massingberd's euphemism for a flasher.