I like ease, so my favorites are all in ones and all in twos with natural fibres inside. Cotton velour is so gorgeous and soft. My favorite AIO's are the type with the attached fold out booster as they dry a lot faster and seem to work/fit better.
Im also starting to love fitteds recently but usually only use them when we can go coverless at home, otherwise when you add the cover they are a bit of a pain and too bullky.
Wool is my favourite for covers hands down. I like the lovey-bums pull on ones as they are so trim and leak-proof. They're the only wool I have tried which can be worn under regular pants when going out. But I love doing laundry and find hand-washing therapeutic
I used to used mostly one-size pockets, but now I hate anything sized. Last time when we first switched to cloth DS was big enough (5 month) to go straight to the largest setting. But with DD I realized its way to much of a pain to be constantly adjusting and keeping track of what size she needs them set to. I also hate the synthetics! So my one-size stash has become my large size stash instead now.
Prefolds and flats are just way too much work to get on a wriggly baby. They would be my last choice when it comes to cloth.