Siblings in Onkyo's Muse range, so they share a design and a house sound. It comes down to power, features and price.
| Area | Better | Why |
|---|
| Power | A | Onkyo Muse Y-50 has more power - 125W against 75W into 8 ohms. That is about 2.2dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Grip on hard loads | evenly matched | Both behave much the same into 4 ohms - output nearly doubles (250W and 150W). |
| Noise floor | evenly matched | Much the same signal-to-noise ratio (100dB vs 100dB). |
| Built-in DAC | evenly matched | Both have a DAC on board with much the same capability. |
| Streaming | evenly matched | The same streaming platforms and services on both. |
| Room to grow | A | Only Onkyo Muse Y-50 offers a subwoofer output - which decides whether you can add a subwoofer or a power amplifier later without replacing the box. |
| Room correction | A | Onkyo Muse Y-50 has room correction. In an awkward room that does more for the sound than any other difference on this page. |
| Price | B | Onkyo Muse Y-40 costs less - $1,000 against $1,500 at list. |
A Onkyo Muse Y-50 B Onkyo Muse Y-40
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?
The usual trade-off: Onkyo Muse Y-50 measures better, Onkyo Muse Y-40 costs about 33% less. With most speakers in most rooms that gap is smaller in practice than it looks here. 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-50 has the headroom, and headroom is what stops an amplifier hardening up on peaks. At desk distance or in a small room, 75 watts is already more than most people ever use, and the extra 50 watts would be headroom you pay for and never hear. Think about the whole system: the roughly $500 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.