Short answer: the Bose Soundlink Flex 2nd gen. It ranks #37 of 179 medium speakers by sound quality (rated 3.8/5) at $159 and is still sold new; the EarFun Uboom Slim ranks #43 (rated 3.7/5) and is discontinued, so it is only an option used.
What the Bose Soundlink Flex 2nd gen does well: A small, rugged waterproof speaker with clear, well balanced mids, app EQ, aptX Adaptive and stereo pairing with a second unit. It supports aptX Adaptive Bluetooth, which the EarFun Uboom Slim lacks. It has an adjustable EQ, which the EarFun Uboom Slim lacks. Watch for: One Flex remains mono and cannot deliver genuine low-bass rumble; RTINGS also found the elevated treble can turn hi-hats and other high-frequency detail piercing.
The EarFun Uboom Slim is the longer-running pick. A slim, affordable waterproof stereo speaker with long battery life that doubles as a speakerphone. It is rated for 16 hours of battery against 12 for the Bose Soundlink Flex 2nd gen. It keeps a wired aux input, which the Bose Soundlink Flex 2nd gen lacks. It plays in stereo from a single unit, unlike the Bose Soundlink Flex 2nd gen. The catch: Not as deep bass as others.
Buy the Bose Soundlink Flex 2nd gen. It is rated higher for sound quality and still sold new, while the EarFun Uboom Slim is discontinued.
Still deciding? The full Portable Bluetooth rankings cover every ranked option.
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Specifications Side By Side
| Bose Soundlink Flex 2nd gen | EarFun Uboom Slim | |
|---|---|---|
| Price | $159.00 | $79 Discontinued |
| Ranked | #37 of 179 in Medium Size Portable Bluetooth Speakers | #43 of 179 in Medium Size Portable Bluetooth Speakers |
| App | Yes | No |
| Battery Life | 12 hours (Manufacturer specified) | 16 hours (Manufacturer specified) |
| Built-in Microphone | Yes | Yes |
| EQ | Yes (3 band) | No |
| IP Rating | IP67 | IPX7 |
| Party Mode | Yes (Bose Party mode) | - |
| Power Input | USB-C | USB-C |
| Stereo | No | Yes |
| Omnidirectional | No | No |
| TWS | Yes | Yes |
| Weight | 1.3 lbs (586 g) | 1.2 lbs (560 g) |
| Bluetooth | Yes | Yes |
| Bluetooth Version | 5.3 | 5.2 |
| Dimensions | 7.9” x 3.5” x 2” (201 x 90 x 52 mm) | 2.6”H x 7.1”W x 2.6”D (65 x 180 x 65 mm) |
| Aux Input | No | Yes |
| Drivers | 60mm full-range driver with passive radiators | 45mm speaker drivers |
| Bluetooth Codecs | SBC, AAC, aptX Adaptive | SBC |
| Digital Aux Input | No | No |
| Strap | Yes (built-in loop) | - |
| Bass Extension (-10dB) | - | ~63Hz |
| Amplifier Power | - | 20W |
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