Sorry, I made a mistake.
Just consider there are 2 situations:
1. n -> pi*
2. pi -> pi*
The energy gap between n & pi* is lower than that of between pi & pi* in most cases.
If electronic transitions are energetically favoured, this implies that n -> pi* transitions are more favourable than that of pi -> pi* transitions due to less energy is required.
However, the intensity of transitions is depend on molar absorptivity (molar extinction coefficient), epsilon, and independent to delta E.