Please nairalanders I want you guys to throw more light on this topic, you never can tell you may be helping someone. You can share your experience too.

what is the credit load

An A or B.

If it is a low credit course, E is acceptable but if a major Credit Load course that will negatively impact your CGPA then...
If the E is because you didn't prepare well or you made a lot of avoidable mistakes, then you would prefer a carry-over. Else you may still fail the carryover.

Neither

My school doesn't have such grade E is either you pass excellently, A or you pass with a lesser score B, at least be on average, C after those three the next is D which the least you could pass with, after D the next result is F.
But getting a carryover in a course is better than the mediocre score E, carryover will give you another opportunity to read harder and who knows you might score A or B when u rewrite such course, which will positively impact your CGPA. But the result E will only make a negative impact on your GP, the only situation when you could manage such result in a course is when you are in your final year and you know that rewriting such exams means extra semester or extra year for you, then you just leave it like that.

Regardless of the course unit, it's best to have at least a C if you are doing it again. Because having a D at the 2nd attempt is equivalent to having a E at the first attempt.

The question is, how would that make you a millionaire?

My brother if You get A or B na bad thing If you know you cannot have both then alway strive to have C OK? Never settle for less....

I think if the student is in a strait, E would be a better option because F is also a grade.

E is 1pts*Course unit
F is 0pts*Course unit

Moreover even if you have an E (not an F) in a course, you can always re-register the course again if you think you can do better at a second attempt. It will only add to the TNU which will be divided by the total score(pts*Course unit) to give the GPA or CGPA as the case may be. Although I think this is subject to the school's discretion.
In my school, even if a student have a D, he can always re-register the course sometimes later if he thinks he can do better, it will only add to the academic load.

My point, of two evils choose the lesser.