You're listening is to the wrong people. No worries with either 6 volts or Futaba servos.
You may see a bit of twitching on a full charge, but it'll go away shortly as the battery drains a bit.
Compared to 4.8 volt packs of the same milliamp size, expect the pack not to stay charged as long due to the higher voltage.
On the plus side, you'll get faster servo response time and more torque.