I find it much better here is my list why
You can make more cause of the budget
There is a magnet
There is duplication
There are now Gravity Volumes
The maps are bigger and better
You know what you are picking up (its highlighted green)
Compared to Halo 3
It is easier to make large maps (my opinion)in halo 4
There are more weapons in halo 4
Even though Halo Reach is the second most recent game its forge is harder to use than halo 4, but still usable
So from what i have experienced halo 4 has the BEST forge. Keep in mind some of this is my personal opinion