What are the differences between major Linux distributions? Will I notice?

I’ve been using Linux in some form intermittently for the past ten years or so, but have only really been in to it for the past few months.

What are the major differences between distributions? Ultimately I know that package management and branding are the big ones, but would it be easier to do task x with distribution y? Why so?

Solution:

I think two main difference is

  • Package management
  • Default Window Manager (Gnome, KDE, XFCE)

Just pointing to these two big difference will somewhat change your behaviour in doing task.For example you could easily install a package on Ubuntu using apt but not so simple when using rpm. Having a difference in Window Manager can also change how you interact with the system.