At the moment you don't have a lot of traffic, so you likely don't have a lot of users, and you don't really know if you have something they'll pay for. You don't really know what problems they experience using your app. You don't really know where else in the process they might fall out of the funnel. Putting the CC requirement at the beginning will even further restrict the flow of users through your funnel and make it harder for you to learn where your stuff is broken.
When you do have traffic, A/B test to find out which one works better for you BTW: there is likely more than one axis with which you'd measure what is "better". You'll have to decide for yourself what those are. Is it better than you have less tire-kickers and more seriously committed users? Is it better to have more people in the funnel in total so you can optimize the trial experience? Is it better to have pre-authorized the credit card and remind them that you're going to start charging them tomorrow if they don't cancel their account?