Large amounts of tile entities affect FPS negatively. When the tiles have more data stored in them, the framerate seems to drop more, eventually to the point where the game is unplayable.

To reproduce:
Use this command:

/fill ~ ~ ~ ~-40 ~ ~-40 minecraft:standing_sign 12 replace {Text1:"Hello"}

and note the FPS before and after. The screen should noticeably stutter as well.