I'd honestly spring for the S9+ if only for one thing: the bigger battery! Performance of the device is great, and doesn't suffer from the slowdowns typical of earlier Samsung phones over time. Display is fantastic, camera is quite good (though a bit below the Pixel 2 / 3 and the Huawei Mate 20 Pro), and battery life is fairly good on the S9+.
As for the negatives, if you want the latest version of Android or a stripped-down experience, this isn't the phone for you. That said, Samsung has actually been doing pretty good with security updates lately (keeping within 30-60 days of Google on that one). Some people also hate the curved screen, though there's an app called "Edge Touch" in the Galaxy Apps store that lets you set up zones where it won't detect touch input.
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