The ebay ones are very limited in what they do. ie: they will clear codes but not show you the description of what they are/were, you cant recode modules etc...
If your just looking to clear the faults, it'll do the job just fine
What about when you set your airbags off after being covered in snow from a lorry and smashing into a squirrel on the hard shoulder?! wont reset the airbag lights!