Hello and howdy!
Before I kick the discussion off, allow me to introduce myself: I go by Kae, and I am a fairly new member in the poniverse! When it comes to fanfiction, I often type up one-shot fics on my spare time, but I have never had the confidence to post my work, for I am a terrible self-critic.
Anyways, I've often wondered whether or not the brony community had a consensus concerning original and canon characters. In your opinion, is one more favorable to you than the other? Whether you have the perspective of the writer or the reader, I am sure you prefer one over the other.
Personally, I am biased towards canonical fiction as a reader. When executed well, the characters are fleshed out beautifully in dynamic situations that the show cannot tackle. However, the introduction of original characters is not "bad," in fact, I find many OCs charming. But regarding one over the other? Canon characters in fanfiction win all the way!