based on the survey towards prefered word counts in fics, below you'll find a quick summary of the basic results. for more detailed evaluations, please check out the document linked below to access the summaries and descriptions to every specified word count shown.
I especially recommend doing this as the ratio comments|votes is not the same!
please note that all of this is subject to personal interpretations. doing this, I tried my best to remain neutral and objective while evaluating and summarizing the replies I received.
as I've observed the graphs adjusting during the process of receiving replies, I found myself fascinated with the changes. in the beginning, the tendency leaned towards 10-50k, then morphing towards 0-15k, until we reached the current results displayed up above.
the most preferred count definitely is 5-30k of readers, spanning 67-60% in order, followed by 30-50k (48%) and below 5k (42%), each with their own reasonings to, the same you'll find explained in more detail in the document linked up above.
comparing this to the graphs for the writers, where the struggles lie at below 5k (35%) and 20k and upwards (41% and upwards), it is also the 20k upwards mark where the disparities begin and where I see the point at which us writers can start making a change.
the graph above is little more than a guide to know what people like more or less. it might help in case you're uncertain of what type of fic to go for first and foremost, yet should under no circumstances derail you from writing what you want.
one-shots are a preferred method but heavily dependent the count of word each fic contains. most readers do prefer a count of 5-20k which is usually the length of a one-shot which explains the connection.
chaptered fics are a welcome option too, yet I want to point out that a lot of answers given stated they prefer regular updates on fics. if you want to go for a chaptered fic and are worried about reader interaction, personally I recommend pre-writing 70% before you start publishing. the reader interaction will get you through the remaining 30% of writing while posting, whilst the regular updates might get more people interested in on-going fics as well.
I heavily emphasize that, albeit series might appear less favored, they are especially useful for connecting one-shots of the same universe but portraying different characters.