Criteria you've specified:
- Powerful enough
Anything you want to consider? The most affordable is VirtualBox because it's free.
The most powerful?
I don't have any hard data on which performs the best but when I had to make the choice (last year) between the three applications to run on my MacBook Pro I chose Parallels.
At the time Parallels seemed to have better support for Windows 8 and 8.1 (better performance than either VirtualBox or VMware). The graphics processing and rendering was far better than the others which meant I could play Windows games on my Mac if I wanted to and most importantly it supported the Retina resolution for the virtual OSes and VMware didn't do that. For me Parallels was powerful enough.
The problem I have now with Parallels is they release a brand new paid version every time Apple releases a new version of OS X. That means within a year the software is "out of date" and all existing (mainstream) support for the product stops. I don't want to spend $50+ a year in upgrades, although I might have to when Windows 10 comes out.
The problem I had with VirtualBox was it didn't do Retina display scaling (at the time), didn't have the same graphical processing capabilities (not sure if that's still true) and I thought I would use the better OS X integration (embed Windows apps in OS X) - but I never did. VirtualBox is that one application I keep around in-case something doesn't work in Parallels.
I've never tried VMware but for me it sits in between the other two - unless they've recently made some gains or offer better features. I think there's a $10 difference between Parallels ($80) and VMware ($70).
As long as you have a powerful enough machine underneath the hypervisor I think you'll be fine with any of them. I'd double-check your criteria before buying something.