Hello again,
The 723 has a built in transistor for current limiting, but it is not as accurate as we need sometimes. The question then becomes, just how accurate do you need to set the current and how stable does it have to be with temperature?
The LM317 can regulate current down to 1.25v with a little external circuitry, but again the question is how accurate do you need to set the current?
You can also get the regulation down to 0.000v with a little trick, if you can stand to loose around two diode drops from your main power supply.
So the question you need to think about is just how accurate do you need to set the current, and how stable does it have to be with temperature...
ie very stable, somewhat stable, not too stable, and what do you intend to use the power supply for...small stuff like LEDs or large stuff like charging batteries. The circuit depends a lot on these criteria, as the number of parts goes up with the more accuracy and stability you need.