Is the Tavor better than the M4? If not, why did the Israelis go to all the trouble and cost to replace their free M4s?
"The TAR-21 design was created by Zalmen Shebs, with the express purpose of creating a weapon more suited to urban combat than the M16/M4 carbine."
Being much more compact in length than the M4/M16 is no doubt beneficial in the urban combat that Israeli forces so often find themselves in (and is also quite useful for getting in/out of the confines of vehicles). Other than that, I doubt there is any other huge advantage over the M4.
That said, adoption of the Tavor has a LONG way to go before it fully replaces the M4/M16.