Chunk handling has become much more intensive and many 1.9 servers can't handle it for long. Movement becomes very choppy and some chunks are also invisible when logging in or teleporting in the world.

http://timings.aikar.co/?url=15263802
http://timings.aikar.co/?url=15264222

Also See:
https://www.spigotmc.org/threads/lag-in-1-9-timings.127420/