I think it's mainly a matter of personal preference towards the user, and as such, since cPanel is the more known and more popular control panel, cPanel will be the choice. I've used both, and cPanel is a little bit easier to use, more laid out and generally shows all the features to control in an organized manner. I didn't mind DirectAdmin either, but the way it was set up really didn't appeal to me. I was using a reseller account too (I find it easier to organize multiple websites) and I must say, WHM is MUCH stronger then the DA reseller panel. Much more organized and generally, better.
I think you will be better to stick with cPanel, unless you can offer DA on the side as well.