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 | Denon DRA-900H has more power - 100W against 75W into 8 ohms. That is about 1.2dB, which is a small step in loudness but real headroom on peaks. |
| Built-in DAC | evenly matched | Both have a DAC on board with much the same capability. |
| Streaming | evenly matched | The same streaming platforms and services on both. |
| Analogue inputs | B | Marantz Stereo 70s takes more analogue sources - 3 against 2. |
| Room to grow | evenly matched | The same expansion options on both. |
| Price | A | Denon DRA-900H costs less - $799 against $1,000 at list. |
| Watts per dollar | A | Denon DRA-900H is the cheaper watt - about $8 per watt against $13. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Denon DRA-900H B Marantz Stereo 70s
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?
Denon DRA-900H has the edge on paper, though not by much. The rows marked "depends" are more likely to decide this than the score is.
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.