What is the best configuration for a Triple System?
On a new Mac (presumably one that uses an Intel i5 or better processor), I think the hassle of rebooting to use BootCamp outweighs the benefit. I would run both Ubuntu and your favorite flavor of Windows in one of the Virtual Machine products. Some prefer VirtualBox because it is free. I'm not in that camp, and I think it has poorer performance than the competing solutions. That leaves Parallels or VMWare Fusion. I've used both, and find little difference between them in real-world usage. I use VMWare Fusion, myself. I would purchase whichever one you can find at a discount. I note that you can often find Parallels included in the Mac software bundle deals that pop up several times a year.