If you get the mass produced plastic ones they are never in tune and simply go out of tune more very quickly. Ceramic ones are often hand made and are properly tuned, they last longer and have a much better sound. Sure you can buy a cheap plastic replica but the high pitched noise will just drive you insane.

Edit:
In the next twilight princess
*zelda chime* you got the cheap plastic ocarina, use it to induce migranes in your enemies!

__________________
i have FULLY completed and i mean fully completed Oot, Alttp, Oos, Ooa, La, Loz (1st quest), Mc, WW, MM, Aol
and i almost forgot FSA although it really isn't a Zelda game
pending: Loz (2nd quest)

Inuyasha to Kagome: "take it [clothing] off"

Favourite anime:
Naruto, Bleach, InuYasha, FMA, Love Hina, Eureka 7, Ai yori Aoshi +/- ~enishi~