We looked at them all and to be honest, they all suck, just in different ways. We are currently with ReadyTalk, which in my opinion, offers one of the best user experiences for the attendee, but is a pain to administer as the webinar owner.
My suggestion is to try several and see which is the best fit for your organization. You'll also want to look at the rest of your marketing stack. Do you need the webinar platform to integrate with anything? If you run marketing automation, finding a tight integration can save hours of work and enable a better experience for the end user.