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 C 368 BluOS-2i has more power - 80W against 60W into 8 ohms. That is about 1.2dB, which is a small step in loudness but real headroom on peaks. |
| Room size | depends | We rate NAD C 368 BluOS-2i the better fit for a mid-size room, a large room and a very large room, and Primare I15 MM for desk or near-field listening and a small room. Match the amplifier to the room you actually have, not the one you want. |
| Grip on hard loads | B | Primare I15 MM holds up better into a 4-ohm load: its output increases strongly to 100W, where the other barely increases. That matters with demanding speakers far more than the 8-ohm figure does. |
| Noise floor | evenly matched | Much the same signal-to-noise ratio (98dB vs 97dB). |
| Built-in DAC | A | NAD C 368 BluOS-2i has a DAC on board; the other needs an external one, which is another box, another power lead and another purchase. |
| Streaming | A | Only NAD C 368 BluOS-2i has AirPlay 2, Roon and BluOS. |
| Analogue inputs | B | Primare I15 MM takes more analogue sources - 5 against 2. |
| Room to grow | evenly matched | The same expansion options on both. |
| Headphones | depends | Only NAD C 368 BluOS-2i has a headphone output. Worth something if you listen late, nothing if you never do. |
| Shelf space | depends | Primare I15 MM takes up about 35% less shelf area (1200cm² against 1840cm²), and it is 83mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | evenly matched | Priced within a few per cent of each other. |
| Watts per dollar | A | NAD C 368 BluOS-2i is the cheaper watt - about $25 per watt against $33. 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 Primare I15 MM
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 368 BluOS-2i has the edge on paper, though not by much. The rows marked "depends" are more likely to decide this than the score is. If your speakers are a difficult load - 4 ohms nominal, big woofers, or a sensitivity in the low 80s - Primare I15 MM is the safer partner, because how an amplifier behaves when the impedance drops matters more than its 8-ohm rating. If you already own a DAC or a streamer, the built-in one is money you are paying twice for, and Primare I15 MM becomes the more rational buy.
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.