No 3D Touch
As expected, one thing the iPhone SE will lack compared to the iPhone 8 is support for 3D Touch, but for all intents and purposes this should be irrelevant now that Apple has introduced Haptic Touch in iOS 13, which provides enough of the same features that most users are unlikely to notice the difference.
With Apple having moved on from the world of 3D Touch last year, it would have been very peculiar for the iPhone SE to still include the feature, which has now become something of an anachronism.