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 110W into 8 ohms is under 1dB, which is not an audible difference in loudness. |
| Analogue inputs | B | Marantz Cinema 50 Series 2 takes more analogue sources - 5 against 4. |
| Phono stage | depends | Marantz Cinema 50 Series 2 has a built-in phono stage and Sony ES STR-AZ3000ES 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 | B | Only Marantz Cinema 50 Series 2 offers preamp outputs - which decides whether you can add a subwoofer or a power amplifier later without replacing the box. |
| Price | A | Sony ES STR-AZ3000ES costs less - $1,998 against $3,000 at list. |
| Watts per dollar | A | Sony ES STR-AZ3000ES is the cheaper watt - about $18 per watt against $27. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Sony ES STR-AZ3000ES B Marantz Cinema 50 Series 2
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?
Marantz Cinema 50 Series 2 is ahead, but on only 1 of the measured areas, and it costs about 50% more. That is a lot of money for a narrow margin - Sony ES STR-AZ3000ES is the sensible buy unless a specific feature above decides it for you. If you play records, Marantz Cinema 50 Series 2 saves you buying a phono stage; if you do not, ignore that row entirely. Think about the whole system: the roughly $1,002 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.