Two schools of thought:
1)Bring a single charge so the jury doesn't have any option. Used if you think guilt is unquestionable but jury may not want to go for the kill.
2)Bring multiple charges so the jury can pick the one they can all agree on. Conviction must be unanimous.Used if jury is expected to vacillate, a lesser conviction is better than an acquittal.
Bottom line it is a judgement call by the DA and what the DA is looking to achieve (and not all DAs want to win sadly).