Gladiator
Beast are better in the current meta because the tempo leans on the direction of a turbo format. Turbo formats play very limited amounts of removal cards, such as
Mirror Force, BTH, D Prison, etc. This leans of the favor of Gladiator
Beasts. They also rely heavily on
spell/
trap cards as win conditions and as drawing engines. Both Glad
Beasts and 6 Sam have decent answers to this (Heraklinos/Shien). 6 Samurai work about this same in Turbo formats and Control Formats. In Turbo Formats, they have little to contend with if and when they go off. In control formats, they tend to be fast enough to catch people off guard and can still hang in slower paced games.
In other words, in control formats, Samurais are good and GB sucks, in turbo formats, GB are amazing and Samurai are good.