Is punching someone and killing them better than shooting them and killing them? The court does. The government does. But I say no. It's still killing. The authorities must do something about this. 90 people have been killed by one punch and the offenders have gotten away with a small prison sentence or fine! This is outrageous and something must be done!
Consequence of a crime is never the ONLY decisive criteria determining degree of punishment they deserve. Motives, regretful or not, etc., can all increase or reduce punishment. e.g. Driving accident. Why one punch killers are getting less punishment than gun killers, are likely due to 1) They didn't expect victim will die with one punch. 2) Because their primary motive wasn't as determined to kill someone as a gun criminal does, it's more likely for them to regret their unintended action.