Title says all.

I have no clue. so I'm going to let the experts tell me

 

"Better" is relative.

But in a technical sense, the 13B-REW is better as it is more evolved as it is the newer engine from the 3rd gen RX-7, while the 13B-T is the engine from the 2nd gen RX-7.

Off hand, the REW is better because:
-better chrome on the rotor housings
-stronger rear casting
-better intake manifold design with modern electronics
-improved front torrington bearing setup
-modern serpentine belts

The turbo system, well that's another discussion entirely.

 

The 13BT is a single turbo from the 2nd Gen RX7, while the 13B-REW is sequential twin turbo from the 3rd Gen RX7. Power wise from stock, the 3rd Gen engine produces more power, ranging from around 255HP-276HP.

 

Depends on how the motor is setup by the owner.

 

13b is better

 

13b

 

I believe the 13bT is a MAS system, while 13bREW is MAP. Some feel the MAP is easier to work with when modding.

Gee, I wonder if I'm impartial?

VVVVV

 

Systems with an AFM though are far harder to blow up than with speed density.

Until the OP clarifies what he means by "better", who knows...