Being the scientist I am, I needed a more "apples to apples" comparison of the one-size diapers in my stash. So I stuffed and set all my one size diapers to their smallest possible settings and measured from the center of the back elastic to the center of the front edge with the tape measure following the inside of the diaper. I then repeated this process with the diapers set on the largest setting. All of the diapers are fairly close in size, but some are more adjustable than others (for example the Fuzzi Bunz with the numbered button elastic, or the Wonder Wrap which offers 4 rise settings). Below are my findings: (sorry I couldn't format a table as I wanted)
Diaper: smallest setting (in.), largest setting (in.)
bumGenius 3.0 Organic: 12, 15
Knicker Nappies Side Snap: 13, 16
GroBaby: 12.5, 14.5
Blueberry: 13, 17
Fuzzi Bunz: 13, 16.5
WonderWrap (Diaper Cover only): 12, 18
I don't know if there is anything conclusive you can extrude from this data considering how close all of the values are. I guess you should just take the data at face value. The only one that raises a flag for me would be the GroBaby, having only a 2" difference in size range were most of the others have at least a 3" difference. I really want to love the GroBaby, but it is just falling a little short. It is to bad, especially seeing how they are now selling a biodegradable/compostable soaker pad that would be great on vacations were you wouldn't have access to a washing machine.
Oh well, I'll figure out what works for me (hopefully soon!) In the mean time I get to try out a new prototype from Kissaluvs. They are expanding their line and it is really exciting! I have to check with them before I post an actually info. In the mean time you might want to check out their website to look at their new Marvels line. The patterns are adorable!