Thanks for the answer, It already has an index on the localdatetime.
It was more a question about internals, like if localdatetime comparison is slower that int comparison.
The comparison would likely be a bit slower, simply because in the difference of the types. A ms timestamp is an 8 byte long (all of Neo4j's numeric values are 64-bit, despite the integer language in the docs), vs a 12-byte value for a localDateTime (8 byte epoch second + 4 byte nanoOfSecond). If you're trying to wring out whatever gains you can, then sticking with ms timestamps makes sense.
That said, this kind of choice would usually be made on ease of use. If all you need to do is raw comparisons and range lookups, then a timestamp works just fine. If you want easier access to inner time components, or make use of durations, then using the native temporal types makes more sense.