Don't know, but buying a $100 case to fix a design flaw in a $80 keyboard seems a bit silly. I tried fixing it by padding the case with foam sheets, it worked a bit, but I could still notice it flexing.
As for the Pure/Poker, it's down to personal choice, I'd look at the layout and see which looks better to you. Bear in mind that the Pure has a short right shift which might make finding replacement keycaps a bit more difficult (most GB's include the short right shift these days, but usually for extra cost).
Another thing to consider is the modabiltiy of the Pure; there is only 1 switch mounted LED (on the FN key) on the Pure (there are 6/7 on the Poker) which means you can switch change the entire board without desoldering any switches. This was a massive bonus to me (and totally unexpected, I can't believe nobody has mentioned it yet) as I like to change switches quite a lot. I was able to change my entire board from reds to clears in about half an hour.