Most people park daily drivers on the solid tiles. From what I've read, there is no issue with this. I would bet the big reason for ordering slotted tiles would if you have floor drains. Otherwise, you're better off getting the solid tiles. If water gets through the seams, it will drain out under the RaceDeck tiles (providing your slab is angled for such) as they are designed for this.
I went with RaceDeck CircleTrac tiles for my garage and I will be parking cars in there with rain and snow on them.
BTW, before I ordered my RaceDeck, I got samples (all solid tiles) from every vendor I could find. I plan on posting up a thread with pictures for comparison purposes once I get the time.