bumgenius are my favorite. the fit is fantastic, they hold brilliantly, and i find my kiddos stayed/stay more comfortable longer wearing them than when wearing their prefolds/covers (e.g. i feel fine about allowing 3 hrs between changes instead of 1.5, or whenever i know the dipe is wet or dirty). however, if you can buy one-size (like bumgenius), used, or seconds, all the better because pocket diapers can be more of an inve$tment than other styles.
for the extra laundry and clothes i had to buy even after my most dilligent folding efforts, i found prefolds to be deceptively inexpensive at the front end. the savings from switching to fitteds was more than made up for in those terms. i really like the fit and durability of one-size bella bottoms diapers. i didn't try any bella bottoms covers, though, because our prowraps (discovered only after too many disasters with other brands without those magically strong gussets!) were a great value and real workhorses around here before we got all spoiled using bumgenius! (perhaps if we had the prefold/prowrap combo at the beginning, i could have nicer things to say about prefolds...?)
regardless, my favorite online sources change according to sales i can find posted on diaperpin.com and via email/online/yahoo groups to which i've subscribed (very easy to do & great savings, btw). my favorites in the past have been mom's milk boutique, nicki's diapers, abby's lane, and cotton babies.
hth!