Sound differences between the DT1770 Pro and T5p 2nd Generation are quite big,
The DT1770 is more fun sounding with more bass quantity and also impact,
The T5p 2nd Gen are more neutral and balanced, yet still retain excellent articulation and body.
The T5p 2nd generation are airier sounding, also more detailed and refined, yet the DT1770 Pro still sounds open for a closed headphone.
Both are excellent headphones, it is a matter of taste.