Advantages.
For aircraft at heavy weights, the higher speed is more efficient.
Dis-advantages.
Potential bird strikes.
Recall some years ago noticing an Ethiopian 727 at Khartoum, parked on the ramp.
The large bird had penetrated the radome, forward pressure bulkhead, FD entry door, and the remains of said bird were in the FC lounge.
Not a pretty sight, for sure.
The idea of 340KIAS at 4000agl may not be all that good for ones health, with big birds (feathered variety) in the vicinity.
