The only one I've used was the python approach. It worked very well for a standalone application which read data from the arduino's serial port and used a somewhat advanced GUI application to display this data back to the end user.
This is particularly useful if you just want to add flare to an embedded project where you're gathering data from a sensor. See here for a basic example.
Given that I haven't tried the other two I can't really comment on which is best, but I will say that since I already had python installed, it took me about 30 minutes to get a working setup where I printed a value over serial to the PC and then had a 'real-time' graph of it on my monitor. Also, given how many awesome scientific libraries there are for python through numpy I can't imagine there would be any data/signal processing that you wouldn't be able to do in python. So those are both two huge pluses for the python route in my book.
Best Answer
Dunno which one is the best, but I really liked DuinOS when I played with it a while back.
It didn't quite work right out of the box and required some tweaking, but I don't remember it being difficult to use.