the arguement over Bio´s has been going on for ever,
Most Bio´s on the market are made from Potasium Biocarbonate ( starch ), tho some companies have and are producing Bio´s made from Dextrose, if you are playing in a humid enviorment, the sugar based Bio´s will give you problems, the break down extremely fast, and can give you a sticky mess in the mag and Hop-Up.
When they first came out on the market, they were crap, just like any new innovation or change in the world of AS, it took a while for the Manufatures to work out the kinks and to start delivering a better product.
Most brands of Bios on the market today are on the same level with High Performance BB´s, you still get the Floater or Drifter, but theare delivering the same good performance.
Remember, as a rule, you get what you pay for, if you go cheap, chances are you are going to be getting terrible BB´s.
The rule for what determines a Bio BB is,
Breaks down to it´s basic components alone with no chemical help,
Non Toxic
Does not damage the Enviorment.
Bio´s are covered with a Wax coating that is biodegradable, it can lead to a build up inside the barrel, this is remedied by cleaning the gun after every game or match week end.
More and more Playing Fields and Event Organizers are requiring the mandatory use of Bio´s, and in my opinion, it just makes sense. Think how a field will look if you have a couple of hundred players there every weekend, sending a few thousand BB´s down range during a game, then to add a little more agravation, kneel down on those little buggers, you don´t have to do hit hard to experiance a good dose of pain.