Pockets are pretty much always going to be bulkier than AIOs, although you can stuff them with trim inserts. Our trimmest diapers are Tots Bots Easy Fits and BG Elementals. Flip diapers (with the stay dry inserts) are pretty trim as well.
Married to my best friend 6/5/10
BFP #1 9/7/10, EDD 5/14/11, Violet born 5/27/11.
BFP #2 4/9/12, EDD 12/16/12, M/C Rory 4/24/12.
BFP #3 10/6/12, EDD 6/16/12., Matilda born 6/17/13.
BG Freetimes, GroVia AIOs and Oh Katy pockets. Fuzzibunz Elite OS pocket and Ones and Twos OS AIO but they both don't even fit my 16 month old 19 lbs LO anymore lol.
Fuzzibunz OS Are the absolute trimmest in my stash, but I'm not a huge fan of them.
Other than that, anything bamboo. I have rainbow BB bamboo, and they are the second most trim. I love anything with bamboo though, the inserts hold so much while they are so skinny!
Grovia AIO's are the trimmest we have. However, my 27lb 12 month old is just squeezing into it on the largest setting. It also has to be changed very frequently. BG elementals are my favorite because they are decently trim, but can hold in a LOT more than the Grovias. Also, the BG has a lot more room for growth. I also have a kissa AIO, but it is more like a pocket with insert sewn in, and I don't think it is much trimmer than BG elemental.
Re: Least bulky aio or os?
BFP #1 9/7/10, EDD 5/14/11, Violet born 5/27/11.
BFP #2 4/9/12, EDD 12/16/12, M/C Rory 4/24/12.
BFP #3 10/6/12, EDD 6/16/12., Matilda born 6/17/13.
Fuzzibunz OS Are the absolute trimmest in my stash, but I'm not a huge fan of them.
Other than that, anything bamboo. I have rainbow BB bamboo, and they are the second most trim. I love anything with bamboo though, the inserts hold so much while they are so skinny!