One is a streaming all-in-one and the other is an amplifier. Judge them on how many boxes you want and what you already own, not on the spec sheet alone.
| Area | Better | Why |
|---|
| Power | A | Denon Home Amp 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. |
| Grip on hard loads | B | Marantz Stereo 70s holds up better into a 4-ohm load: its output nearly doubles to 150W, where the other increases modestly. That matters with demanding speakers far more than the 8-ohm figure does. |
| Built-in DAC | evenly matched | Both have a DAC on board with much the same capability. |
| Streaming | evenly matched | Only Marantz Stereo 70s has Roon. Neither list is longer in a way that matters - check the one service you actually pay for. |
| Phono stage | depends | Marantz Stereo 70s has a built-in phono stage (MM) and Denon Home Amp 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 | evenly matched | The same expansion options on both. |
| Amplifier class | depends | Denon Home Amp is Class D and Marantz Stereo 70s is Class A/B. Class D runs cool and draws almost nothing at idle; Class A/B runs warm and is the long-established mainstream choice. Modern examples of both measure well - judge by the rest of the page. |
| Shelf space | depends | Denon Home Amp takes up about 68% less shelf area (580cm² against 1803cm²), and it is 142mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | A | Denon Home Amp costs less - $899 against $1,000 at list. |
| Watts per dollar | A | Denon Home Amp is the cheaper watt - about $9 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 Home Amp 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 Home Amp has the edge on paper, though not by much. The rows marked "depends" are more likely to decide this than the score is. If your speakers are a difficult load - 4 ohms nominal, big woofers, or a sensitivity in the low 80s - Marantz Stereo 70s is the safer partner, because how an amplifier behaves when the impedance drops matters more than its 8-ohm rating. If you play records, Marantz Stereo 70s 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.