The petal type are that shape for a reason - designed for a specific lens to avoid vignetting - the corners of the image being cut off by the lens hood. You tend to get this type with wide angle lenses and some zooms where you can get vignetting just at certain zoom positions.
You're probably best going for the proper one for your lens. The rubber adjustable types are OK, but you need to check in the shop - fit the hood, stop down to a small aperture, and use the depth of field preview button to see if there's any sign of vignetting in the viewfinder.