Two versions of the same amplifier rather than two different designs, so the question is not which is better built but which set of features you actually need - and what the difference costs.
| Area | Better | Why |
|---|
| Power | evenly matched | Effectively the same output - 200W against 200W into 8 ohms is under 1dB, which is not an audible difference in loudness. |
| Grip on hard loads | evenly matched | Both behave much the same into 4 ohms - output nearly doubles (380W and 380W). |
| Noise floor | evenly matched | Much the same signal-to-noise ratio (120dB vs 120dB). |
| Built-in DAC | evenly matched | Both have a DAC on board with much the same capability. |
| Streaming | evenly matched | The same streaming platforms and services on both. |
| Room to grow | evenly matched | The same expansion options on both. |
| Price | B | NAD Masters Series M33 costs less - $6,499 against $7,399 at list. |
A NAD Masters Series M33 V2 B NAD Masters Series M33
depends neither is better in the abstract - it turns on your room, your system or how you will use them. Only specs published for both amplifiers are judged; anything missing on either side is left out rather than guessed.
Which should you choose?
Neither runs away with it - they trade advantages. Let the "depends" rows and the speakers you already own settle it.
What a spec sheet cannot show: how either sounds with your speakers, how the controls feel day to day, and what the app is like to live with - which is where most all-in-one amplifiers are actually won or lost. Power figures are the manufacturers' own and are not measured to a common standard, so treat small differences as noise. If you can hear both, that will tell you more than any row above.