7h3 5u65717u710n 0f num63r5 f0r l3773r5, 45 1n 7h15 53n73nc3. The difference between numspeak and 1337speak is that numspeak simply involves substituting numbers for letters in otherwise gramatically correct english, whereas 1337speak also incorporates lots of internet slang terminology.
1337speak: 0MFG! U ju57 g07 pwn3d by my h34d5h07! 1 4m 73h 13377357 h3x0r 1n t3h w0r1d!