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 | evenly matched | Effectively the same output - 70W against 60W into 8 ohms is under 1dB, which is not an audible difference in loudness. |
| Speaker load rating | B | JBL MA310 is rated down to 4 ohms against 6, so it is the safer partner for a low-impedance speaker. |
| Analogue inputs | evenly matched | The same number of line-level inputs (2). |
| Room to grow | evenly matched | The same expansion options on both. |
| Built-in sources | depends | Denon AVR-S570BT has a radio tuner built in. That is one less box if you still play discs or listen to radio, and dead weight if you do not. |
| Amplifier class | depends | Denon AVR-S570BT is AB and JBL MA310 is D. Class A/B runs warm and is the long-established mainstream choice; Class D runs cool and draws almost nothing at idle. Modern examples of both measure well - judge by the rest of the page. |
| Price | evenly matched | Priced within a few per cent of each other. |
A Denon AVR-S570BT B JBL MA310
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?
JBL MA310 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.