I've done some more comparing with normal Lua vs LuaJit using WorldEdit's //sphere command.
As expected there is only a noticeable change when doing large stuff.
EDIT:
This does include reading and writing to the world.
Code:
| Lua 5.1 | LuaJit | NumBlocks changed
//sphere glass 5,7,6 0.029999999999973 | 0.023 | 1367
//sphere glass 10 0.090999999999894 | 0.062999999999999 | 4169
//sphere glass 40 5.983 | 3.988 | 267761
As expected there is only a noticeable change when doing large stuff.
EDIT:
This does include reading and writing to the world.