Let me share with you my personal experience. Since 1998, both offices have operated independently, but prior to that time, counsel worked for the prosecution as well as for the defence.
There are certain differences today. However, to say that the prosecution has a tougher job, I would answer that they have more work to do because they must compile solid evidence. Occasionally, they must ask law enforcement officials for additional evidence, but both sides work with the same documents. Defence counsel spend as much time reading documents submitted as do counsel for the prosecution. Asking for new investigations to be carried out may involve a little more work, but it's all the same as far as we are concerned. Fewer delays are encountered, however. There is also the fact that witnesses must be tracked down. In many cases, medical evidence must be found, which means meeting with doctors and so forth.