Buy for a Regular Fingerprint Sensor
The Galaxy S10 and S10+ use a new ultrasonic fingerprint reader that is under the screen. This is new tech, but so far the reviews are good. That said, maybe you prefer a traditional fingerprint reader like on older Samsung phones.
If you like the older style fingerprint reader, buy the Galaxy S10. Instead of putting this on the back or under the screen it is on a button on the right side of the phone.
This isn't a reason for everyone, and it definitely shouldn't be your only reason for buying the Galaxy S10e, but it is something to consider alongside the rest of the reasons.