Which is more scoring? I have to drop one of them...

NOTE: my programming is weak...

Not sure what you mean by "scoring", but I would say 3CL4 is the harder of the two. You don't need to be amazing at programming to get by in 2SI4, a lot of it is based on larger structures and concepts that you can understand in a more general/theoretical concept.

Depending on your program, you may have to take both before you graduate anyways..

If you drop si4, you'll hate your life, if you drop cl4 you'll get better grades.
Units are both rated at '4' as you can see (meaning a grade of x in one is the same as in the other), so unless you're in a hurry to do a course thath as 3cl4 as s prereq, get rid of si4.

Cheers.