These are not the same size of amplifier: Onkyo Muse Y-40 has roughly 2.5x the power of Onkyo A-9110. That is about 4dB, 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 | Onkyo Muse Y-40 has more power - 75W against 30W into 8 ohms. That is about 4dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Noise floor | B | Onkyo A-9110 is the quieter design on paper - 103dB against 100dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | A | Onkyo Muse Y-40 has a DAC on board; the other needs an external one, which is another box, another power lead and another purchase. |
| Amplifier class | depends | Onkyo Muse Y-40 is Class D and Onkyo A-9110 is Class A/B. Class D runs cool and draws almost nothing at idle; Class A/B runs warm and is the long-established mainstream choice. Modern examples of both measure well - judge by the rest of the page. |
| Shelf space | depends | Onkyo Muse Y-40 takes up about 15% less shelf area (1225cm² against 1434cm²). |
| Price | B | Onkyo A-9110 costs less - $349 against $1,000 at list. |
A Onkyo Muse Y-40 B Onkyo A-9110
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?
Onkyo Muse Y-40 is ahead, but on only 1 of the measured areas, and it costs about 2.9x the price. That is a lot of money for a narrow margin - Onkyo A-9110 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 - Onkyo Muse Y-40 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 45 watts would be headroom you pay for and never hear. If you already own a DAC or a streamer, the built-in one is money you are paying twice for, and Onkyo A-9110 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.