No single best amplifier here. What decides it is what you have to drive, what you need to plug in, and how much of the system you want in one box.
| Area | Better | Why |
|---|
| Power | A | Denon AVR-A10H has more power - 150W against 120W into 8 ohms. That is about 1dB, which is a small step in loudness but real headroom on peaks. |
| Analogue inputs | A | Denon AVR-A10H takes more analogue sources - 6 against 3. |
| Phono stage | depends | Denon AVR-A10H has a built-in phono stage and ARCAM AVA25 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 | A | Only Denon AVR-A10H offers preamp outputs - which decides whether you can add a subwoofer or a power amplifier later without replacing the box. |
| Built-in sources | depends | Denon AVR-A10H has a radio tuner built in. That is one less box if you still play discs or listen to radio, and dead weight if you do not. |
| Price | A | Denon AVR-A10H costs less - $5,199 against $5,500 at list. |
| Watts per dollar | A | Denon AVR-A10H is the cheaper watt - about $35 per watt against $46. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Denon AVR-A10H B ARCAM AVA25
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?
Denon AVR-A10H has the edge on paper, though not by much. The rows marked "depends" are more likely to decide this than the score is. If you play records, Denon AVR-A10H 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.