The following is my opinon, which is based on having handled and currently owning versions of both of various types of Super Oysters. First, double check but I believe that Will and TungChoy use some of the same suppliers for some of their products, so some might be the same thing. Both are quality sellers. With TungChoy, you'll get better variety and with will you will get FAR more personal attention. Also TungChoy ships from Hong Kong, while Will ships from Canada.
As for the super oysters, they generally come in 22mm and 20mm varieties; in straight or curved ends. Both sets come with the option of using regular or fat springbars (though you are probably best off getting one that takes fat springbars and using a spacer for use with regular spingbars). The curved end ones come with an adjustable open endcap tat is made to fit a wide variety of cases. with some adjustment it will fit the slimmed down base seiko diver case. Several Sellers who also sell the bracelets, also offer custom end caps made to fit specific cases (Will, Yobokies and Swedefreak come to mind). Of these, IMHO the best of all the endcaps for the 6309-7040 are the heavy gauge open endcaps sold by Swedefreak, that are made for the Super oyster. Will also sells these together with the bracelet.
There is a new version of the Super oyster called the MkII, which comes either in straight 20mm width or starts at 22mm and narrows to 20mm at the clasp. the original Super oysters came at 20 or 22mm and narrowed to 18mm at the clasp. You can see pictures and a review of the MkII SO here:
http://www.thewatchsite.com/index.php/topic,165.msg235.html#msg235
IMHO for the 6309-7040 the best balanced combination is the MkII super oyster, with seiko's springloaded flip-lock clasp with 4 microadjustment holes, with Swedefreak's endcaps and made to take fat seiko springbars.
Do keep in mind that the metal used on the screw pins can sometimes be a little soft, and over torquing the pins can result in stripped threads. be firm but gentle when resetting the pins. This is true of all Super oyster models I have tried.
Hope that helps.
