Let's get this out of the way--the style of the Marshall is either a love-it or hate-it affair. If you're keen to the Marshall amp motif or have live music in your blood, the physical appearance of this speaker should fit your needs; and let's face it, style points typically do count for purchases like these. In this case, you really do get something special beyond the spate of all-plastic futuristic-looking cylinders, boxes, spheres and pillboxes that seem to typify most Bluetooth speakers today.
But how does it perform? I've got the Bose SoundLink Mini and Klipsch KMC-3 and KMC-1 Bluetooth speakers at home and work for comparison. Say what you will about Bose, but they DO know how to squeeze an amazing amount of sound out of tiny enclosures. Does the Marshall do better than the Bose at filling a room with a pleasant, snappy, punchy sound--well, sure it does, but it's got acres more driver and juice in the amp to do so; as such, it's hardly surprising that the Marshall seems to be able to fill larger spaces without sounding as strained as the Bose starts to at higher volumes. But would you be unhappy with the Bose over the Marshall, not at all--especially if a small form factor was your goal.
The Klipsch KMC series speakers are no slouches either--I'd put sound quality of the KMC-1 below the Bose, but the KMC-3 above them both in terms of liveliness and punch and ability to fill medium to larger rooms with less effort. The KMC-3 is probably the most direct competitor to the Marshall in terms of size and total output capability. So how do those two stack up...honestly, it's a bit of a toss-up. The Marshall probably sounds a tad more "full bodied" at louder volumes, but each seems to resolve vocals and instruments with equal aplomb. Both the Klipsch and Marshall lines support the aptX Bluetooth codec so overall sound quality is maybe just a hair more refined/revealing on the Klipsch KMC-3 and Marshall speakers than the Bose. Personally, I kind of prefer the Marshall's actual knobs and switches to either the Klipsch or Bose touch-sensitive panels or soft membrane buttons--but again, that's more a matter of personal taste though. I did find that Bluetooth pairing was much easier with the Marshall and Bose than the Klispch units.
All that said, frankly, critical listening comparisons and flowery descriptions of a single-speaker system using a Bluetooth connection to listen to streaming audio or even high quality MP3 files isn't necessarily a "high fidelity" experience in the first place. Others may disagree, but I find you can't really talk in depth about, or expect to talk about, all those things/terms you read about in stereo magazines and hifi websites with any real authority--transparency this, imaging that, transient highs...blah blah blah. Not that those things aren't legitimate issues to talk about, but music consumption/listening is so subjective anyway; you're likely going to hear something completely different than I would even when listening to the exact same setup.
Sure, some speakers might empirically sound like the bass is a bit "muddy" or "over-emphasized" or the highs a little "too bright" or maybe "de-emphasized" and that might all be part of the unit’s “signature sound”. For the Marshall, it’s not as easy to pin that signature down, and a big part of that is being able to adjust both bass and treble to your liking with the Marshall's adjustment knobs...you can do neither with the Klispch or Bose units. In my book, that alone makes the Marshall slightly more versatile than any of the other units…again, at least in my opinion. In the end...no, the Marshall is no substitute for a great set of bookshelf speakers and a fantastic amp, but that's not what it's designed for in the first place. All that said, the Marshall has a heck of a lot going for it…would I recommend the Marshall—absolutely, it kicks butt!