The newer ST and FT bindings seem to have much better brake units… that is they actually seem to release reliably compared to the aftermarket stuff that you could fit to Comfort and Speed bindings. Actually there doesn’t seem to be much differences but Dynafit seem to have made some changes that make the brake units actually work. (Lou Dawson had some information on the brake problems on http://wildsnow.com/ at one time).
If you are going to be resort skiing I would go for brakes and as Peter says leashes and avalanches are a concern.
I was at Dynafit the other day and they told me that their research suggests that women skiers prefer brakes, one reason being is that the give a more stable platform for putting skis on. This makes sense, legion are the people who have lost skis during this manouvere. For this reason the ST White binding (for the girls) only comes with brakes fitted.
Arguments against: some weight and a brake won’t stop your ski on a steep slope. I actually lost a ski in a steep couloir and the brake unit, broke! Recovered my ski at the bottom without a brake.