what is the best small block and why ?

In my opinion ( in stock form) the early 340s are the best mopar small blocks hands down. First of all they have a forged crank. 360s have cast cranks ( weaker). the early 340s are also higher compression,(10.5) a than 360. 340s have a shorter stroke so they wind higher in RPM. Now this is not to say a 360 is a bad motor, as they can be made to run great too, but in stock form the 340 is the real performer here. In the last several years it has become popular to stroke these small blocks, from 408 to 416 and even bigger, which is fine because they make great torque when stroked. I would say both the 340 and the 360 strokers are fairly simular in performance.