Two versions of the same amplifier rather than two different designs, so the question is not which is better built but which set of features you actually need - and what the difference costs.
| Area | Better | Why |
|---|
| Power | evenly matched | Effectively the same output - 85W against 80W into 8 ohms is under 1dB, which is not an audible difference in loudness. |
| Analogue inputs | B | ARCAM AVR11 takes more analogue sources - 6 against 3. |
| Room to grow | B | Only ARCAM AVR11 offers preamp outputs - which decides whether you can add a subwoofer or a power amplifier later without replacing the box. |
| Built-in sources | depends | ARCAM AVR11 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. |
| Amplifier class | depends | ARCAM AVA15 is D and ARCAM AVR11 is AB. 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. |
| Price | B | ARCAM AVR11 costs less - $3,050 against $4,500 at list. |
| Watts per dollar | B | ARCAM AVR11 is the cheaper watt - about $38 per watt against $53. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A ARCAM AVA15 B ARCAM AVR11
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?
ARCAM AVR11 is the easier recommendation: it leads on most of the measured areas and costs less. Take ARCAM AVA15 if one of the "depends" rows above describes your system. Think about the whole system: the roughly $1,450 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.