We loved our original DI - but new versions are less powerful. We also have the Ultimate Decadent Indulgence - it has just 3 AAs and lacks the power to drive both strong vibes and rotation. The DI2 & DI3 are 2AA models so I'm going to guess they also lack power.
We prefer to use a dildo or vibrator for penetration and a really strong clit vibe instead of the 2-in-1 models. Our current favorite combination is Johnny Vixskin with the Mimi or Mystic Wand vibe.