In short, between the iPad 2 and the new iPad (retina):
- Weight: Same
- Thickness: Same
- Screen: Yowser! The old screen looks pixellated and blurry, the new screen is brilliant. Also a lot warmer.
- Performance: Same
Between the original and the new iPad (retina):
- Weight: Oh, so much lighter
- Thickness: Oh, so much thinner
- Screen: As above, but the original was warmer than the iPad 2.
- Performance: Blazingly faster, yet the original is still no slouch.