Well, since you are asking for "opinions"......you spoiled me by creating that smooth flat surface and now hanging either set of vents in there looks a bit like making the AC register in your home become the focal point of the wall. If I had to choose, I'd go with the round ones because the rectangles just look too 70's for that dash, but what about hiding the vents behind a smooth panel that retracts when you want AC? Hmmm....... you know what they say about opinions....