I know some people reccomend the Net breeders, but i dont, this is why:
The framing on the inside can crush the fry, when they hide under or beside them. breeder boxes do not have this, and you can clearly see the fry by looking into the tank, rather than having to look in the top.
The net keeps all crap and un eated food inside it. where as with the breeder boxes they have small slots in the bottom, which you can just lift slightly out of the water and put back in for a water change and clean!
The nets can only be placed were there metal clips alow, and to a certain water level, breeder boxes float, can be moved to any position in the tank, and sits on any water level.
Fry can be picked of through net breeders by bigger fish such as angels, but they cannot be caught through the breeder boxes. I know some say that they can be picked of through the slots in the bottom, and that is true with the big breeder boxes, but if you get the guppy breeder boxes, (i will find exact brand soon) the slots are too small for this, and i have watched my angels many times try get at fry and never had success.
These breeder boxes are smaller, and are a little bit more expensive ($10) but i think the above warrents enough reason for purchaseing one or two. I am always useing mine, to grow up very small fry and other things.
If it were me i would never purchase another net breeder. however some people sware by them, in the end it is up to the aqauriest, and ill leave it at that.
Shae