Different price classes - Onkyo TX-RZ70 costs roughly 1.7x what Denon AVR-X2900H does. Expect it to lead on paper; the question is whether you will hear the difference through the speakers you own.
| Area | Better | Why |
|---|
| Power | B | Onkyo TX-RZ70 has more power - 140W against 95W into 8 ohms. That is about 1.7dB, which is a small step in loudness but real headroom on peaks. |
| Analogue inputs | evenly matched | The same number of line-level inputs (4). |
| Room to grow | B | Only Onkyo TX-RZ70 offers preamp outputs - which decides whether you can add a subwoofer or a power amplifier later without replacing the box. |
| Shelf space | depends | Denon AVR-X2900H takes up about 29% less shelf area (1559cm² against 2205cm²), and it is 148mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | A | Denon AVR-X2900H costs less - $1,349 against $2,300 at list. |
A Denon AVR-X2900H B Onkyo TX-RZ70
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?
The usual trade-off: Onkyo TX-RZ70 measures better, Denon AVR-X2900H costs about 41% less. With most speakers in most rooms that gap is smaller in practice than it looks here. Think about the whole system: the roughly $951 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.