The Top Ten Olympia & Avantguard Headguards are all all AIBA approved. The only difference is whether you want to pay extra for the AIBA sticker that adds unecessary cost to the items here in the US. They are made of the same patented Bayflex rubber that was tested in the Technical University of Berlin study. FYI - At the AIBA Boxing Championships held in Chicago last summer, the TOP TEN Headguard (boxing version covered in leather) was mandatory equipment.
I've used the Olympia and the Avantguard and prefer the fit of the Avantguard. I didn't believe the hype until I used one myself. The best test is to put one on (the correct size) and have someone punch and kick you and see what you think.
The best place to purchase the products in the US is at
WWW.TOTIRO-USA.COM. They are the actual supplier for the TOP TEN products sold on everyone else's websites.