The Diablo Mid has more of a classic box beam feel to it -- think POG, PS 85 etc. The Blade 93 does not have that same box beam solidness, but it feels faster, snappier and more responsive.
The Diablo Mid has a livelier stringbed, but both offer about equally forgiving sweetspots. I would say the Diablo is a little more topspin friendly, the Blade 93 more precise and a slightly better slice racquet. Both a great sticks and the differences are not that major when it comes to what I can do with the ball when playing with either.
The ROK has exceptional feel, but is a fair bit lower powered than the other two. It offers a softer feel and requires more from the player to get the ball away.
I would be totally happy playing a tournament with either the Diablo Mid or the Blade 93, I like both that much. The ROK not so much.