Gravity is more like a firmer JK Pro than DX in my experience.
for the record (for me at least), the new DX Roc3s I have are pretty much what I might consider stiff JK-ish. So the comparison to harder JK and DX might be saying the same thing ? That said, I dont think its across a whole run of DX. Just my Roc3s as my Thunderbirds are very hard.