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 | B | NAD C 388 has more power - 150W against 80W into 8 ohms. That is about 2.7dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Room size | depends | We rate NAD C 368 BluOS-2i the better fit for desk or near-field listening, a small room and a mid-size room, and NAD C 388 for a large room and a very large room. Match the amplifier to the room you actually have, not the one you want. |
| Grip on hard loads | evenly matched | Both behave much the same into 4 ohms - output barely increases (80W and 150W). |
| Noise floor | A | NAD C 368 BluOS-2i is the quieter design on paper - 98dB 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 C 368 BluOS-2i has AirPlay 2, Roon 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. |
| Price | B | NAD C 388 costs less - $1,499 against $1,749 at list. |
| Watts per dollar | B | NAD C 388 is the cheaper watt - about $10 per watt against $22. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A NAD C 368 BluOS-2i B NAD C 388
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. 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 388 has the headroom, and headroom is what stops an amplifier hardening up on peaks. At desk distance or in a small room, 80 watts is already more than most people ever use, and the extra 70 watts would be headroom you pay for and never hear - we rate NAD C 388 poorly for near-field use for exactly that reason.
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.