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 | JBL MA710 has more power - 110W against 70W into 8 ohms. That is about 2dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Speaker load rating | A | JBL MA710 is rated down to 4 ohms against 6, so it is the safer partner for a low-impedance speaker. |
| Analogue inputs | B | Yamaha RX500A takes more analogue sources - 3 against 2. |
| Phono stage | depends | JBL MA710 has a built-in phono stage and Yamaha RX500A 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. |
| Built-in sources | depends | Yamaha RX500A 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 | JBL MA710 is D and Yamaha RX500A is AB. 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 | Yamaha RX500A takes up about 17% less shelf area (1396cm² against 1672cm²), and it is 65mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | B | Yamaha RX500A costs less - $600 against $880 at list. |
A JBL MA710 B Yamaha RX500A
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 47% more. That is a lot of money for a narrow margin - Yamaha RX500A is the sensible buy unless a specific feature above decides it for you. If you play records, JBL MA710 saves you buying a phono stage; if you do not, ignore that row entirely. Think about the whole system: the roughly $280 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.