Why use a transistor for getting a Constant Current Source in a circuit with an op amp?
If you don't need a true ground on the load and the load is not remote then the first circuit is preferable (an example would be an integrator where the load is a capacitor). It would not be great if the load was a temperature sensor with 20m leads. 

The transistor circuit has the load grounded, will work even if the load is below the V- of the op-amp. It has less compliance in the positive direction (only works up to V+ -Vref + 100mV or so), and somewhat lower output resistance, but in practical applications it's most often a much better choice (at least when implemented correctly, as LvW points out!).