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 | evenly matched | Effectively the same output - 120W against 145W into 8 ohms is under 1dB, which is not an audible difference in loudness. |
| Room to grow | A | Only McIntosh MHT300 offers preamp outputs - which decides whether you can add a subwoofer or a power amplifier later without replacing the box. |
| Built-in sources | depends | McIntosh MHT300 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 | McIntosh MHT300 is D and ARCAM AVA35 is G. Class D runs cool and draws almost nothing at idle; Class G/H switches its supply rails to cut the heat a Class A/B design wastes. Modern examples of both measure well - judge by the rest of the page. |
| Shelf space | depends | ARCAM AVA35 takes up about 14% less shelf area (2070cm² against 2421cm²), and it is 67mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | B | ARCAM AVA35 costs less - $7,000 against $9,500 at list. |
| Watts per dollar | B | ARCAM AVA35 is the cheaper watt - about $48 per watt against $79. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A McIntosh MHT300 B ARCAM AVA35
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?
Neither runs away with it - they trade advantages. Let the "depends" rows and the speakers you already own settle it. Think about the whole system: the roughly $2,500 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.