wow, now this is tricky, it's certainly a contest between F-A+ and 1-5 and whilst both have their own advantages and disadvantages i believe i'm going to go with the F-A+ option.
1-5 is good, and is most definately useful for when you're deciding on a score for a quick review. obviously 5 choices are smaller than 18 and i feel for the people who are not quite sure on their final outcome, this could be the better option. not only does it provide an easy, fast way of scoring, but it also makes it easier for people to skim down through. sure, people can read B- or C+, but numbers can be deciphered much faster, letting intersted readers immeidiately know you're own thoughts and feelings are on the episode. however, what i believe to be the main disadvantage is that it's just too vague if you're a person who really takes their reviews seriously and wants to give the fairest, closest score possible. imagine if you think an episode is slightly above average, let's say for example the colour yellow. you can't give it a 3, because that's too low, 3 is the average, middle of the road. but then again you can't give it 4 because that's too high and you're giving it too much praise. you could piss around with 3.5's but if thats the case, what's the point of using these numbers anyway, you might as well as start using 3.25 or 3.125.
that's where F-A+ comes in - and it's just better. whilst it might not give someone instant knowledge of your opinion, and might take a bit longer to figure out, it's worth it for it's sheer conciseness. now for the above example, if it's slightly better than average, you could give it not just a C, but a C+, or even a B-, it's gives you freedom, not like the communist styles of 1-5's, you're not held back, you're free to choose for a wide range of options and fit them to your own examples and reviews. it works - it's used by schools, giving a sign of it's clarity and usefulness. if scholars and professionals can use it, why can't we? forget 1-5's, F-A+'s are the way ahead.