I'm a Behat developer.
Why I've developed Behat instead of Cucumber customization:
In terms of features, Behat and Cucumber are almost the same (I've worked hard to achieve this). But in terms of speed/extensibility/logic from a PHP developer's perspective - Behat is better, because it's a fast and clean native PHP tool. Behat is not a Cucumber port, as you might think by first, it's built entirely from the ground on PHP 5.3. Behat is trying to simulate Cucumber with its input reading (features) and output formatting (formatters), but it's not a Cucumber port (there are no Ruby syntax constructions in PHP).