These are not the same size of amplifier: NAD C 379 has roughly 2.7x the power of NAD D 3020 V2. That is about 4.3dB, so it is a question of room size and how hard your speakers are to drive, not of one being the better amplifier.
| Area | Better | Why |
|---|
| Power | A | NAD C 379 has more power - 80W against 30W into 8 ohms. That is about 4.3dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Noise floor | B | NAD D 3020 V2 is the quieter design on paper - 98dB against 95dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | A | Both decode on board. NAD C 379 goes higher - 384kHz against 96kHz. Very few recordings exist above 192kHz, so treat this as headroom, not as sound quality. |
| Use with a TV | depends | Only NAD C 379 has HDMI, so the television can drive it directly and one remote controls the volume. If the system is for music only, this changes nothing. |
| Room to grow | evenly matched | The same expansion options on both. |
| Shelf space | depends | NAD D 3020 V2 takes up about 92% less shelf area (146cm² against 1810cm²), and it is 168mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | B | NAD D 3020 V2 costs less - $499 against $1,099 at list. |
A NAD C 379 B NAD D 3020 V2
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?
NAD C 379 is ahead, but on only 1 of the measured areas, and it costs about 120% more. That is a lot of money for a narrow margin - NAD D 3020 V2 is the sensible buy unless a specific feature above decides it for you. Start with the room. In a large or open-plan room, or with speakers that are hard to drive - low sensitivity, or an impedance that dips - NAD C 379 has the headroom, and headroom is what stops an amplifier hardening up on peaks. At desk distance or in a small room, 30 watts is already more than most people ever use, and the extra 50 watts would be headroom you pay for and never hear. If this sits under a television, NAD C 379 is the one to buy - HDMI ARC means the TV remote controls the volume and there is no second box in the way.
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.