Moving From Lightroom To C1....Question

Quite new here. I'm officially moving to C1 from Lightroom. A while back I converted some images to the dng format. Not the best idea. But anyway now I'm trying to determine if I should export these images in the dng format or as tiffs in order to import into C1. I don't want to do a complete LR catalog import into C1 just a thousand or so key images.Aside from the size of the dng vs tiff files what do you feel are some of the key pros and cons?
Thanks!!!