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 - 110W against 125W into 8 ohms is under 1dB, which is not an audible difference in loudness. |
| Analogue inputs | A | Yamaha AVENTAGE RX-A4A takes more analogue sources - 3 against 2. |
| Room to grow | A | Only Yamaha AVENTAGE RX-A4A offers preamp outputs - which decides whether you can add a subwoofer or a power amplifier later without replacing the box. |
| Built-in sources | depends | Yamaha AVENTAGE RX-A4A 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 | Yamaha AVENTAGE RX-A4A is AB and JBL MA7100HP 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 | B | JBL MA7100HP costs less - $1,320 against $1,600 at list. |
| Watts per dollar | B | JBL MA7100HP is the cheaper watt - about $11 per watt against $15. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Yamaha AVENTAGE RX-A4A B JBL MA7100HP
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: Yamaha AVENTAGE RX-A4A measures better, JBL MA7100HP costs about 18% 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.