I'm somewhat of a layman, but I'd wager A/B pages printed 50:50 (by IP for instance) could lead to a rather solid conclusion if ran long enough. On the other hand, eh, chat bubbles suck and you can quite confidently say they don't help, so might as well keep it this way. On a personal note I do feel like I would be much more prone to click a chat request as another menu option than a bubble.