Short answer: the Soundcore Boom 3i. It ranks #31 of 179 medium portable speakers against the Flex 2nd gen’s #37, at essentially the same price, so there is little reason to pay the same money for the lower-ranked speaker.
The two take very different approaches to sound. The Flex 2nd gen’s own notes say it sounds nearly identical to the original Flex, warm with bass boosted enough to drown out midrange detail, and it is not stereo. It also self-drains about 10% of its battery a week when idle. The Boom 3i’s notes describe it as looking like a direct answer to the JBL Charge 5, with a similar warm, bass-forward tuning at better value, though it does not quite match the Charge 5 for loudness or balance. An early Boom 3i firmware version had some bass distortion that Soundcore addressed in an update through its app.
Everything else is close: neither speaker is stereo, and both lean into a warm, bass-heavy signature rather than a neutral one.
Buy the Soundcore Boom 3i for the higher-ranked sound at the same price, as long as you keep its firmware current.
Buy the Bose Soundlink Flex 2nd gen if you specifically want the Bose ecosystem or form factor and can live with the battery drain and a bass-heavy tuning that overshadows midrange detail.
Looking for alternatives? See the complete Portable Bluetooth rankings.
Prices on this page were last checked November 11, 2026 at 3:26 AM UTC. Product prices and availability are accurate as of that date/time and are subject to change; the price and availability shown on Amazon at the time of purchase will apply to the purchase of this product.
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Specifications Side By Side
| Bose Soundlink Flex 2nd gen | Soundcore Boom 3i | |
|---|---|---|
| Price | $159.00 | $118.99 |
| Ranked | #37 of 179 in Medium Size Portable Bluetooth Speakers | #31 of 179 in Medium Size Portable Bluetooth Speakers |
| App | Yes | Yes |
| Battery Life | 12 hours (Manufacturer specified) | 16 hours (Manufacturer specified) |
| Built-in Microphone | Yes | Yes |
| EQ | Yes (3 band) | Yes |
| IP Rating | IP67 | IP68 |
| Party Mode | Yes (Bose Party mode) | No |
| Power Input | USB-C | USB-C |
| Stereo | No | No |
| Omnidirectional | No | No |
| TWS | Yes | Yes |
| Weight | 1.3 lbs (586 g) | 1.7 lbs (783 g) |
| Bluetooth | Yes | Yes |
| Bluetooth Version | 5.3 | 5.3 |
| Dimensions | 7.9” x 3.5” x 2” (201 x 90 x 52 mm) | 8.3” x 3.3” x 3.1” (210 x 85 x 78.5 mm) |
| Aux Input | No | No |
| Drivers | 60mm full-range driver with passive radiators | 94mm woofer + tweeter |
| Bluetooth Codecs | SBC, AAC, aptX Adaptive | SBC, AAC |
| Digital Aux Input | No | No |
| Strap | Yes (built-in loop) | Yes (detachable strap) |
| Bass Extension (-10dB) | - | 56Hz |
| Amplifier Power | - | 50W |
| Lights | - | Yes |
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