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 | Onkyo TX-RZ30 has more power - 100W against 70W into 8 ohms. That is about 1.5dB, which is a small step in loudness but real headroom on peaks. |
| Speaker load rating | A | Onkyo TX-RZ30 is rated down to 4 ohms against 6, so it is the safer partner for a low-impedance speaker. |
| Analogue inputs | A | Onkyo TX-RZ30 takes more analogue sources - 6 against 3. |
| Phono stage | depends | Onkyo TX-RZ30 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 | A | Only Onkyo TX-RZ30 offers preamp outputs - which decides whether you can add a subwoofer or a power amplifier later without replacing the box. |
| Price | A | Onkyo TX-RZ30 costs less - $1,250 against $1,398 at list. |
| Watts per dollar | A | Onkyo TX-RZ30 is the cheaper watt - about $13 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 Onkyo TX-RZ30 B Sony ES STR-AZ1000ES
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?
Onkyo TX-RZ30 is the easier recommendation: it leads on most of the measured areas and costs less. Take Sony ES STR-AZ1000ES if one of the "depends" rows above describes your system. If you play records, Onkyo TX-RZ30 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.