I wouldn't go by Sharp ratings alone, they are not the be all and end all, although they are helpful. Some people have questioned their testing methods.
The SHARP testing methods were, as I understand it, questioned by Arai when their helmets didn't do very well!!!!
There is no other independent testing available over and above the various mandatory requirements so it's the best out there.
That write-up isn't about
SHARP - they're DOT, ECE 22.05 & Snell, and some of those do tests involving sharp object impacts.
According to the 1990s
COST (Cooperation in Scientific and Technical Research) 327 study, that isn't a very common occurence, hence why manufacturers (and users) doubt the usefulness of some of the tests.
SHARP claims to reproduce & measure more realistic situations, such as glancing blows.
There has been criticism of SHARP as well (
here and
here for example). The main criticisms seem to be that the test head used is not a 'soft' head like a real human, and that the rotation effects aren't measured (
SHARP says otherwise).
However, for all that, as David says, no one has come up with anything better yet.
Some
good advice from SHARP themselves:
Remember, the most important aspect of a helmet is that it provides the right fit for you. It’s not necessarily the highest SHARP rated helmet that will be the best for you if it doesn’t fit correctly. When you are choosing your next helmet, try on as many as you can to find a selection that fit and are comfortable and then consider their SHARP safety rating to make the safest possible choice.Lastly, for amusement since I found it whilst searching just now, here's my helmet (well, not
mine) as
tested by Guy Martin - it's bust bottom left. Good of him to test it for me.