Installing ubuntu 13.04 on mac?

That's more difficult, because Boot Camp doesn't allow you to have more than two volumes on your hard disk: one for Windows and another one for OS X. However, you can install OS X, Windows and Ubuntu in the same hard disk, and Canonical has got the steps to do this > https://help.ubuntu.com/community/MactelSupportTeam/AppleIntelInstallation Note that steps are a bit outdated, so do it at your own risk.

I recommend you to install Ubuntu 13.04 on a virtual machine instead of on the hard disk if you have Windows

Use Oracle VirtualBox or VMware Fusion or Parallels Desktop for Mac

I actually use VMware Fusion 5 for some testing environment and used sporadically VirtualBox in the past. I tried Parallels Desktop some years ago, before buying VMWare Fusion.

What is the best?

Maybe none or all of them it depends on your needs. VirtualBox is free. The others are paying options but have a 30 days trial, Fusion and 14 days trial Parallels.

They all perform similarly... they've all had years to mature at this point. It's more about refinement and "bells and whistles". I prefer VirtualBox primarily because it is free and fully functional. The good thing is that when it gets updated, you can get the latest version without having to pay for an upgrade. I also use it on quite a few machines... Macs and PCs. I don't want to have to worry about licensing multiple machines for a pay product. I will usually recommend that someone try VirtualBox to see if it will meet their needs. It's free, so no harm done if you don't like it. Parallels and Fusion are great products and offer some more features with respect to integration with the host OS. I'm personally not a big fan of that, but that's more of a preference on my part.