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 AVR-S770H has more power - 75W against 50W into 8 ohms. That is about 1.8dB, which is a small step in loudness but real headroom on peaks. |
| Analogue inputs | B | Marantz NR1510 takes more analogue sources - 3 against 2. |
| Room to grow | evenly matched | The same expansion options on both. |
| Shelf space | depends | Denon AVR-S770H takes up about 14% less shelf area (1512cm² against 1753cm²), and it is 51mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | B | Marantz NR1510 costs less - $700 against $749 at list. |
| Watts per dollar | A | Denon AVR-S770H is the cheaper watt - about $10 per watt against $14. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Denon AVR-S770H B Marantz NR1510
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: Denon AVR-S770H measures better, Marantz NR1510 costs about 7% less. With most speakers in most rooms that gap is smaller in practice than it looks here.
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.