GitHub User: jipiboily
I've made some short testing and capybara-webkit is still around 20% faster in our use case. I suggest you try it for yourself and see, that's a matter of minutes or hours if run longer tests to have better metrics.
Just for the sake of new visitors, Rails has changed quite a bit during the last 4 years. Here's how you could do it now:
class ApplicationController < ActionController::Base
rescue_from Whatever::Exception, :with => :whatever_exception
# do something here
Here's some basic guide (official)