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 | Naim Uniti Star has more power - 70W against 40W into 8 ohms. That is about 2.4dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Room size | depends | We rate Naim Uniti Atom the better fit for desk or near-field listening and a small room, and Naim Uniti Star for a mid-size room, a large room and a very large room. Match the amplifier to the room you actually have, not the one you want. |
| Built-in DAC | evenly matched | Both have a DAC on board with much the same capability. |
| Streaming | evenly matched | Only Naim Uniti Star has AirPlay 2. Neither list is longer in a way that matters - check the one service you actually pay for. |
| Analogue inputs | evenly matched | The same number of line-level inputs (1). |
| Room to grow | evenly matched | The same expansion options on both. |
| Built-in sources | depends | Naim Uniti Star has a CD player built in. That is one less box if you still play discs or listen to radio, and dead weight if you do not. |
| Shelf space | depends | Naim Uniti Atom takes up about 43% less shelf area (781cm² against 1371cm²). |
| Price | A | Naim Uniti Atom costs less - $3,799 against $5,699 at list. |
A Naim Uniti Atom B Naim Uniti Star
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?
Naim Uniti Star is ahead, but on only 1 of the measured areas, and it costs about 50% more. That is a lot of money for a narrow margin - Naim Uniti Atom 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 - Naim Uniti Star has the headroom, and headroom is what stops an amplifier hardening up on peaks. At desk distance or in a small room, 40 watts is already more than most people ever use, and the extra 30 watts would be headroom you pay for and never hear - we rate Naim Uniti Star poorly for near-field use for exactly that reason. Think about the whole system: the roughly $1,900 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.