They are similar is style (narrow crotch, high rise) but different too. Fireflies are serged and have the fold out soakers (have you seen one? Do you know what I'm talking about?). Fuz have bound edges, an internal soaker, and a doubler. FF's snap in the front w/ 2 snaps that are next to each other, Fuz snaps are on top of each other. Fuz also come in more sizes, like medium, whereas FF's are only sm and large (and xs and xl too).
I think the Fuz dipes are more "substantial" but w/ a doubler I think FF's are just as absorbant.
ETA that Fuz are flat in back (no elastic) and FF's have back elastic.
pbandj described the differences very well. Also, the ff only come in colours in the S and L sizes, while the fuz is all sizes. Also, the sizing is different - the L ff is comparable with other WAHMs larges, while the fuz L is HUGE - it's even bigger than most XL's. So make sure to check the sizing charts.
As far as aethetic appeal - the fuz wins out every time. They are just gorgeous and the colours are so vibrant. I love the coloured ff's, too, but dd is getting larger than the larges (LOL!) so I'm soon out of colour-range. Unfortunately, the binding on the fuz does wear very quickly and it's maddening to see a $30 fuz with ratty edges. I've been religiously hanging them to dry and it's prolonging them a bit but they are still unraveling. The fuz dry about the same as other internal soakers but man those fireflies dry quickly!
All in all, I would recommend buying one or two really special fuz and any others be coloured fireflies. The ff are much more practical, workhorse dipes (while still being beautiful) but the fuz are just gorgeous.
Forgot to mentione the sleeptight ff - they are wonderful! By far my favourite night dipe. I also use a L fuz with an extra doubler for night and it works great. But the firefly with a pull-on wool cover is the best night system I've found yet.
I'm glad to hear you describe the FFs as "good workhorse dipes" because that's exactly what I'm after. I had a used FF I got off the TP, and I liked it so I just got a few new ones so I can use them more often and make sure they are really what I'm after. My plan is to sell off most of my other fitteds and use the $$ to build a stash of mostly FFs, because they work so well under clothes for the winter. That would be a pretty nice stash, huh? My DH is afraid to ask how much they cost.
I have decided I will satisfy my hyena cravings with beautiful wool covers from now on. (Although, I did buy a cute FLAG last night.
Hee hee! FFs and lovely wool covers! And to think that when I first started CDing I pitched the concept of "saving money" to my DH! So much for that, huh??
I only have 2, but I just ordered 4 more and a nighttime one to try. I will have 3 each of the cotton (yummy soft) and the cotton/hemp (more absorbent). They are so trim. I love them. I have found that around the house if I put a wool liner in them, I don't need a cover and then when I do need a cover because they are so trim, they're still not bulky at all. I love all the colors, too.
I'm anxiously awaiting the postman to see if my ffs came today!!!!
I'm glad to hear the nighttime one is great. The description Lori gave of it sounded wonderful. Right now we're using a SP with a Joey Bunz under the doubler folder over for the boy zone and an Aristocrat and that's working, too, but it's nice to have options.