How We Research
We compare products from their published specs and features; the verdicts below are our independent editorial opinions.
If you want one pair of headphones to cover travel, commuting, and hours of wireless listening with active noise cancellation, choose Amazon Renewed Marshall Monitor III; if you need precision-tuned, low-latency wired in-ear monitors for competitive FPS gaming, choose Sony INZONE E9.
• Marshall Monitor III biggest strength: Up to 70 hours of wireless playtime with ANC on, 100 hours with it off, in a foldable over-ear design with a hard case.
• Marshall Monitor III biggest trade-off: It's a Renewed unit, so it carries a 90-day limited warranty rather than a full manufacturer one, and its appeal is music listening, not competitive gaming.
• Sony INZONE E9 biggest strength: A sealed, noise-isolating in-ear design co-developed with Fnatic, with 7.1ch virtual surround and EQ tuning through the INZONE Hub.
• Sony INZONE E9 biggest trade-off: It's wired only, so you're tethered to your device, and the fit depends entirely on getting the right eartip seal.
• Pick Marshall Monitor III if you want wireless freedom, ANC, and long battery life for music and travel.
• Pick Sony INZONE E9 if you want a wired, low-profile monitor built specifically for hearing footsteps and callouts in shooters.
The Monitor III is, at its core, a travel and daily-listening headphone. The headline number is 70 hours of wireless playtime with active noise cancellation engaged, stretching to 100 hours with ANC off. That's the kind of figure that means you can fly cross-country, work a full week of commutes, and still not think about the charging cable. For anyone who has owned over-ears that die by mid-afternoon, that spec alone reframes how you use them.
The over-ear build is where the comfort argument lives. Soft ear cushions, a rugged shell, and a foldable hinge that tucks into a supplied hard case make this a headphone you can throw in a bag without babying it. Marshall also upgraded the ANC on this generation so it continuously measures ambient noise rather than sampling it once, and there's a transparency mode when you need to hear a boarding announcement or a barista. The Soundstage spatial audio feature pushes the mix out of your head for a wider sense of space, and Dynamic Loudness rebalances treble, mids, and bass as you change volume so the low end doesn't vanish when you listen quietly.
Who should buy it: commuters, frequent flyers, and anyone who wants one wireless pair for music, calls, and noise blocking, and who is comfortable buying a Renewed unit backed by a 90-day limited warranty. Who should skip it: competitive shooter players who need a wired, ultra-low-profile monitor, and buyers who specifically want a brand-new retail unit with a full-length warranty. If the Renewed angle gives you pause, weigh it against the fact that the headphones ship with the case, a USB-C charging cable, and a USB-C to 3.5mm audio cord, so you can go wired when the battery eventually matters.
The INZONE E9 is a specialist tool, and it makes no apology for that. It's an in-ear monitor developed with input from Fnatic's esports players, tuned for FPS gaming where the difference between hearing a reload behind a wall and missing it decides the round. The dynamic driver is voiced for clear, sharp detail rather than a warm, bass-forward signature, and the sealed, fully enclosed body with multiple eartip sizes is there to isolate you from the room around you.
The real differentiator is the USB-C audio box. It unlocks 7.1-channel virtual surround and lets you adjust EQ through Sony's INZONE Hub software on PC. That's the part that separates this from a generic pair of earbuds: you can tune the sound to your game and your ears. Add a low-profile shell with flexible ear hooks and four eartip sizes in the box, and you get something designed to stay put through a long session without pressure points. The 16 Ω impedance and 101 dB/mW sensitivity mean it's easy to drive, and the gold-plated L-shaped stereo mini plug plus a slim 1.8m detachable Y-type cable let it sit comfortably under a full-size gaming headset if you double up.
Who should buy it: PC and console players who play competitive shooters, streamers who want their ears free of a headband, and anyone who prefers the isolation of a sealed in-ear fit. Who should skip it: listeners who want wireless freedom or active noise cancellation on a plane, and anyone who wants one pair of headphones for music first. The E9 is wired, passive-isolating, and built around a specific job. It comes with a manufacturer warranty and a compact carrying case, so it's a legitimate grab-and-go kit, just not an all-purpose one.
• Best for battery life → Amazon Renewed Marshall Monitor III. 70 hours with ANC on and 100 hours without is in a different universe from a wired monitor.
• Best for competitive FPS gaming → Sony INZONE E9. It was co-developed with Fnatic, tuned for FPS detail, and supports 7.1ch virtual surround with EQ adjustment.
• Best for noise control on a plane or train → Amazon Renewed Marshall Monitor III. Active noise cancellation that continuously measures ambient noise beats passive isolation for low-frequency engine drone.
• Best for long sessions without ear fatigue on a headband-free setup → Sony INZONE E9. Flexible ear hooks, four eartip sizes, and a low-profile shell are built for that.
• Best for travel convenience → Amazon Renewed Marshall Monitor III. Foldable, over-ear, and it ships with a hard protective case plus both USB-C and 3.5mm cables.
• Best for tuning your own sound on PC → Sony INZONE E9. The INZONE Hub app and USB-C audio box give you EQ and surround control the Marshall doesn't offer.
• Best for buyers who want a full manufacturer warranty → Sony INZONE E9. The Marshall is a Renewed unit with a 90-day limited warranty.
• Best for casual music listening and calls → Amazon Renewed Marshall Monitor III. Dynamic Loudness, Soundstage spatial audio, and a built-in mic make it the more versatile everyday pair.
In my opinion, these two barely compete, because they solve different problems. If I had to pick one for the average buyer reading this, I'd take the Amazon Renewed Marshall Monitor III. It's the pair that works on a plane, on a walk, at a desk, and on a call, and it does it without a cable. The 70-hour ANC figure and the foldable over-ear design are the specs that actually change your day. But if your reason for reading this is ranked shooters, I'd take the Sony INZONE E9 without hesitation: purpose-built tuning, 7.1ch surround, and a fit made for long sessions. Buy the Marshall for how you live; buy the E9 for how you compete.
A Renewed unit is a pre-owned product that's been inspected and repackaged, and it ships with a 90-day limited warranty instead of a full manufacturer term. You still get the hard case, USB-C cable, and USB-C to 3.5mm cord. Check the current price on Amazon and compare it against the new version before deciding.
You can listen to music on them, but they're wired, so there's no Bluetooth. There's also no built-in microphone described in the specs, which means they're not the right pick for calls. They're a gaming-first monitor.
The Marshall Monitor III uses active noise cancellation and continuously measures ambient noise, which is far more effective against constant engine rumble. The E9 relies on passive isolation from its sealed body and eartips, which works well for nearby voices but less so for low-frequency drone.
For competitive gaming, the Sony INZONE E9 wins on tuning, 7.1ch virtual surround, and a stable low-profile fit. For everyday listening, travel, and wireless convenience, the Marshall Monitor III is the more useful pair by a wide margin.
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