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 | evenly matched | Effectively the same output - 165W against 200W into 8 ohms is under 1dB, which is not an audible difference in loudness. |
| Speaker load rating | A | Devialet Expert 220 Pro is rated down to 2 ohms against 4, so it is the safer partner for a low-impedance speaker. |
| Noise floor | A | Devialet Expert 220 Pro is the quieter design on paper - 130dB against 120dB. 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 | B | Only NAD Masters Series M33 has AirPlay 2 and BluOS. |
| Analogue inputs | evenly matched | The same number of line-level inputs (2). |
| Room to grow | evenly matched | The same expansion options on both. |
| Headphones | depends | Only NAD Masters Series M33 has a headphone output. Worth something if you listen late, nothing if you never do. |
| Amplifier class | depends | Devialet Expert 220 Pro is ADH (Analog Digital Hybrid) and NAD Masters Series M33 is Class D. Class D runs cool and draws almost nothing at idle. Modern examples of both measure well - judge by the rest of the page. |
| Shelf space | depends | Devialet Expert 220 Pro takes up about 22% less shelf area (1521cm² against 1949cm²), and it is 51mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | B | NAD Masters Series M33 costs less - $6,499 against $10,000 at list. |
| Watts per dollar | B | NAD Masters Series M33 is the cheaper watt - about $32 per watt against $61. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Devialet Expert 220 Pro 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. Think about the whole system: the roughly $3,501 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.