As Blue Bear says, it's purely a cosmetic preference. They'll do something for absorption...just not very much. I'm talking here as though I actually know something. LOL! The only thing I know is I was dead set on getting foam for the whole darn studio and then I found this place and these great folks. I soon learned that foam was not really the best acoustical choice. For my modest home studio I'm employing Mintraps from Ehtan as well as his cloth covered 703/705 fiberglass offereings. But I do like the looks of foam, so I'm including it too and there's nothing wrong with that I feel. I'm just not looking for much acoustical benefit. I'm using it for a waynescoting type of thing, then using foam block boarder to cap that off, and the rest of the wall surfaces will be treated with mintraps, 703, 705, and 2" foam. The 703, 705 and foam panels will alternate along the walls so I have some color thrown in and also have the great acoustical rewards from the rigid fiberglass. Nothing wrong with foam, as long as you know where you stand with it. All looks, and slight acoustical benefit, and no real difference between eggcrate and wedges, except for the look...and price.
Dan