Posted By:
Shawn AdkinsWow, I was shocked to see TWO active T205 threads this afternoon!
As Joshua mentioned, we collect auction data of all shapes and sizes. In addition to that public data, I also have information from many other collectors as to the cards that reside in their collections.
--Thanks to everyone who has shared their information with me --
The back information Josh provided is absolutely correct unless there are some rare backs that don't show up very often, Broadleaf/Hindu/Drum, as those may never be accurately documented for obvious reasons. Each card has only one back and this is key information when shopping for either version without a back scan. SGC and GAI have the brand listed on the flip and that's all you need to determine which one is which. Why I'm sharing this is beyond me as I still need upgrades for both of mine. 
Taking everything into account for this reponse, my data shows that the correct card has been offered for sale or documented in a collection 2 - 3 times less than it's counterpart. Even though a few of the "suffered" variety have sold recently through various venues, it's still far behind the "suffe ed" version in terms of number of copies documented. The last time I checked the SGC pop report, it showed a 3 to 1 ratio (15 - 5) with the correct version having only 5 graded copies back in early Apr.
My personal opinion is that both cards are among the 10 toughest cards in the set, but their actual placement on that list will be reserved for a future post (or publication). This is based on my collection of over 12,000 documented T205s that I currently have in my database.
Cheap plug -- anyone who has not shared information about their set with me can send an email for an Excel template that makes that documentation very easy. <G> The more data I have the more accurate the reports will become. Back information and back scans are always helpful.
Both of the Wilhelm cards are tough and often remain on wantlists for an extended period of time. The "suffered" version was one of the last five cards achieved in my master set, Thanks again Art!
Shawn