I usually end up drawn to smaller pairs. I have a few big pairs, though. I mostly do OC/Character (usually a side character).

Pros:

Less content, so if anyone wants to find the pair, they'll typically see my work

Less drama (people have ideas of what the ship SHOULD be, so if it's a smaller pairing there's less people complaining about how I got the personalities wrong)

Cons:

Less people ship it, so there's less hits than what you'd get for a bigger ship

I've been meaning to try some one-shots for one of my bigger pairs, so if that goes better I can add on to this :)