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 | B | Yamaha AVENTAGE RX-A4A has more power - 110W against 70W into 8 ohms. That is about 2dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Speaker load rating | B | Yamaha AVENTAGE RX-A4A is rated down to 4 ohms against 6, so it is the safer partner for a low-impedance speaker. |
| Analogue inputs | evenly matched | The same number of line-level inputs (3). |
| Phono stage | depends | Yamaha AVENTAGE RX-A4A has a built-in phono stage and Sony ES STR-AZ1000ES 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 | B | Only Yamaha AVENTAGE RX-A4A offers preamp outputs - which decides whether you can add a subwoofer or a power amplifier later without replacing the box. |
| Shelf space | depends | Sony ES STR-AZ1000ES takes up about 23% less shelf area (1537cm² against 2003cm²), and it is 102mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | A | Sony ES STR-AZ1000ES costs less - $1,398 against $1,600 at list. |
| Watts per dollar | B | Yamaha AVENTAGE RX-A4A is the cheaper watt - about $15 per watt against $20. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Sony ES STR-AZ1000ES B Yamaha AVENTAGE RX-A4A
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?
Yamaha AVENTAGE RX-A4A leads across most of the measured areas for a fairly modest premium, so it is the easier pick if the budget stretches. Sony ES STR-AZ1000ES is the one to take if it does not. If you play records, Yamaha AVENTAGE RX-A4A 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.