When looking into package management systems one is going to want to use the one with the most useful repositories for his/her taste.
You also need to be considering what type of gui you are going to be using as each one has different software that is compatible with each most programs can run on most giu's or at least be recoded/converted to run on said gui.
Something to look into first is what will be more comfortable using there is gnome which closely resembles Windows gui.
Then you have KDE which is largely popular amongst linux user.
You have flux-box which is a minimalistic gui for high end power users and may sometimes be better for box's that need to be able to have more resources free due to it's limitations.
There others but these are the most common also some people (although I would not recommend it to a new user)Who simpley use the CLI (Command line interface)
Remember that no matter what you use you will eventually have to use the CLI and it is recommended that you learn bash scripting or at least get the basics of bash commands down so that it isn't a culture shock when you start using it.
There is a website that I recommend you visit that can give you basics of the bash prompt here:http://www.linux.org/lessons/
I hope this helps.