Which do you prefer and why? Do you use one type or a combination of both...for example, one type for daytime vs. another for overnight?
We are doing prefolds with covers right now, but are probably going to switch over to pockets, AIOs, or a combination of both.
Also, what is the difference between the BG 3.0s and 4.0s?
Thanks!
Re: Pockets vs. AIOs
Pockets. AIOs tend to take forever to dry. Pockets you can stuff as much/little as you want.
BG4.0s only come in pastel colors, and I think the fasteners have been improved upon. You should be able to get a comparison on one of the diaper websites.
I prefer pockets. Like pp said, they dry much faster and I feel they get cleaner too in the wash. And also like pp said, you have control over the absorbancy with adding inserts.
BG 3.0's have been discontinued and replaced with the 4.0's. other than some color changes, you can get the 4.0 in either aplix or snap closures and the 4.0 is suppossed to be slightly bigger to fit babies longer. I use the 3.0's and love them, haven't tried a 4.0 yet since I have no need/excuse to buy another diaper :-(
I like both for different reasons. I like AIOs for ease of use by sitters and grandparents.
I like pockets because they have adjustable absorbancy and they are quicker to dry.
This!
<a href="http://s5.photobucket.com/albums/y161/putalittlepolkainyourdot/?action=view
DD1 born 5/24/10.
Missed M/C at 14 wks Feb 2012.
DD2 born 5/14/13.
Missed M/C at 9 wks July 2015.
I really like both. I used the BG pockets and the BG organic AIO so both one-size. The AIOs are great b/c they're trim and all one piece plus natural fibers. The pockets are great b/c they're velcro and easy to get on/off and change absorbency. Plus faster to dry. I only used prefolds in my pockets, not mf, to avoid stink.
I would normally keep AIOs in the diaper bag since they took up much less room.
I like both.
I have BG organic ("Elemental") AIOs and a GroVia AIO. Both are very trim and very absorbent. In fact, with my DD, who was a super heavy wetter (when she was in diapers), I found that she was less likely to leak in AIOs. With pockets, the insert tended to bunch up, and so she leaked around the legs -- not an issue with AIOs, because they have a sewn-in insert.
But I use mostly pockets with DS right now. Mostly because it's easier to find pockets for cheaper
And he's not a heavy wetter, so leaks aren't too much of a concern. They do take longer to dry than pockets, but I put them in with my prefolds and they are done in one dryer cycle.
As for 3.0's vs 4.0's... the 4.0's aren't available in my favorite bright colors
and the 3.0's aren't available in the new ultra-light pastels. The 4.0 velcro seems a lot stronger, so I think it will hold up better over time. The 4.0's have a loop strip of velcro for laundry tabs, rather than the piece of fabric for laundry tabs that the 3.0's had -- I'm almost certain that those will hold up better over time. The 4.0's have slightly exposed elastic, making it easier to replace when it wears out. The 4.0's have a slightly different shape, which supposedly makes them fit better on larger kids. I keep meaning to try mine on DD to see if that's true
But really, the two versions are more alike than they are different. I like them both equally, except for the lack of bright colors for the 4.0's 
Mommy to DD1 (June 2007), DS (January 2010), DD2 (July 2012), and The Next One (EDD 3/31/2015)