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 | B | JBL MA710 has more power - 110W against 75W 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 (2). |
| Room to grow | evenly matched | The same expansion options on both. |
| Built-in sources | depends | Denon AVR-S670H 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-S670H is AB and JBL MA710 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 | A | Denon AVR-S670H costs less - $649 against $880 at list. |
A Denon AVR-S670H B JBL MA710
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 MA710 is ahead, but on only 1 of the measured areas, and it costs about 36% more. That is a lot of money for a narrow margin - Denon AVR-S670H is the sensible buy unless a specific feature above decides it for you. Think about the whole system: the roughly $231 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.