These are not the same size of amplifier: WiiM Amp Pro has roughly 2x the power of Onkyo A-9110. That is about 3dB, 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 | WiiM Amp Pro has more power - 60W against 30W into 8 ohms. That is about 3dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Noise floor | evenly matched | Much the same signal-to-noise ratio (105dB vs 103dB). |
| Built-in DAC | A | WiiM Amp Pro has a DAC on board; the other needs an external one, which is another box, another power lead and another purchase. |
| Phono stage | depends | Onkyo A-9110 has a built-in phono stage (MM) and WiiM Amp Pro does not. Decisive if you own a turntable, completely irrelevant if you do not - and an outboard phono stage is easy to add later either way. |
| Room to grow | evenly matched | The same expansion options on both. |
| Amplifier class | depends | WiiM Amp Pro 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 | WiiM Amp Pro takes up about 71% less shelf area (420cm² against 1434cm²), and it is 110mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | B | Onkyo A-9110 costs less - $349 against $379 at list. |
| Watts per dollar | A | WiiM Amp Pro is the cheaper watt - about $6 per watt against $12. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A WiiM Amp Pro 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?
WiiM Amp Pro leads across most of the measured areas for a fairly modest premium, so it is the easier pick if the budget stretches. Onkyo A-9110 is the one to take if it does not. 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 - WiiM Amp Pro 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 30 watts would be headroom you pay for and never hear. If you play records, Onkyo A-9110 saves you buying a phono stage; if you do not, ignore that row entirely.
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.