I can call time on this debate - the best oyster is this one, Kumamoto oyster.
Kumamoto Oysters (Crassostrea sikamea) originally hail from (surprisingly) the Kumamoto area of Kyushu in Southern Japan but are also being grown here in Australia.
What you'll immediately notice, when compared to their rivals, is their size - these are small oysters but have quite a pronounced cup which can make balancing them a bit precarious.
The flesh is creamy, buttery and sweet and if you aren't really a great fan of oysters (I put my hand up here) then you really should give these a go as I think you'll be quite impressed.
These are oysters that are best served as nature made them but if you must have something I can highly recommend just a slight scattering of finger lime.
You don't just get the citrus factor which enlivens the flavour you also get those bursts of flavour and texture as the finger lime pods explode in your mouth.
A glass of bubbles and a few of these - life doesn't get much better.