Which A/B test software do you prefer? Howcome?

[ThomasHgenhaven]

I am about to start some research on software for experimental design on websites. So I'd really like to know which A/B test software do you prefer? Howcome?

[TomCritchlow]

Depends on your use case but this is a good resource:

http://www.whichmvt.com/

Personally I really like VWO: http://visualwebsiteoptimizer.com/ I like the way you don't need heavy code changes to run tests.