One is a streaming all-in-one and the other is an amplifier. Judge them on how many boxes you want and what you already own, not on the spec sheet alone.
| Area | Better | Why |
|---|
| Power | A | NAD Masters Series M33 V2 has more power - 200W against 130W into 8 ohms. That is about 1.9dB, which is a small step in loudness but real headroom on peaks. |
| Grip on hard loads | A | NAD Masters Series M33 V2 holds up better into a 4-ohm load: its output nearly doubles to 380W, where the other barely increases. That matters with demanding speakers far more than the 8-ohm figure does. |
| Noise floor | A | NAD Masters Series M33 V2 is the quieter design on paper - 120dB against 95dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | evenly matched | Both have a DAC on board with much the same capability. |
| Streaming | A | Only NAD Masters Series M33 V2 has AirPlay 2, Roon and BluOS. |
| Room to grow | evenly matched | The same expansion options on both. |
| Price | B | NAD C 389 costs less - $1,499 against $7,399 at list. |
| Watts per dollar | B | NAD C 389 is the cheaper watt - about $12 per watt against $37. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A NAD Masters Series M33 V2 B NAD C 389
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?
The usual trade-off: NAD Masters Series M33 V2 measures better, NAD C 389 costs about 80% less. With most speakers in most rooms that gap is smaller in practice than it looks here. If your speakers are a difficult load - 4 ohms nominal, big woofers, or a sensitivity in the low 80s - NAD Masters Series M33 V2 is the safer partner, because how an amplifier behaves when the impedance drops matters more than its 8-ohm rating. Think about the whole system: the roughly $5,900 saved by taking the cheaper one would buy better speakers or a subwoofer, which does more for the sound than the difference between two competent amplifiers.
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.