Both Champion fullbacks
Brett better tackler by a way with copybook tackles, not with his studs
Brett faster yet Slater more elusive
Both exceptional positionally.
I think Brett was part of a physical team and played a little tougher, not calling Slater weak, but he can be ragdolled far easier than Stewart.
Slater makes 100 extra plays off the ball every week and 99/100 times does not get the ball....but it’s the constant threat, how he makes the effort and has the energy to get around the ball all day.
Brett’s freak plays included his team mates on many occasions, where Slater is more a solo act apart from supporting to finish a move, though ball plays at times with a drift across field using his acceleration on a second man play.
All round pretty even, but both at their peak I take Stewart as the overall better player.