In terms of value, I'd lean towards Bryston because unless you're purchasing something super old you're still going to be covered by the warranty and support.
In terms of the sound character you're looking for, there's a reason Bryston is used in so many professional audio setups.
Lastly, to answer your question about the benefits of the newer Cubed models over the previous generation amplifiers, the Cubed amps have even better detail retrieval, clarity of sound, tonal balance, and noise rejection. They just sound better all around, assuming the sound character described above is what you're looking for. I strongly prefer the Cubed versions over the previous generation.
In terms of the sound character you're looking for, there's a reason Bryston is used in so many professional audio setups.
Lastly, to answer your question about the benefits of the newer Cubed models over the previous generation amplifiers, the Cubed amps have even better detail retrieval, clarity of sound, tonal balance, and noise rejection. They just sound better all around, assuming the sound character described above is what you're looking for. I strongly prefer the Cubed versions over the previous generation.