I base the resoning on the observation that in a Corporate world you mostly work on foobared windoze machines. Based on that I Observe the following.
The download size:
Why does it matter? Simply because sometimes you have to work on machines that are locked down, and only connected to extremely slow proxies to the internet.
Python d/l: ~10mb
J2SE ( not the fancy J2EE stuff ): ~50mb
Installation without Admin rights:
Why does it matter? In some places you have to work on machines for which you can't get an admin account ( even as developer ).
Python: Not a problem
J2SE: Impossible to install
Compiling Sources "out of the box":
Why does it matter? Sometimes you get preinstallations for software, java would be such a case. In face that you can't do admin installs, you still could write programms if it only was capable of compiling stuff.
Python ( batteries included ): interpreter/compiler/runtime.
JRE ( tough on most machines preinstalled ): runtime only ( can't develop )