Cold foam is a type of latex that cures at room temperature and does not need to be baked. There are several issues with it though. It tends to be exceedingly porous and the bubbles within the interior are large sometimes leaving pockets. It also must be used in a very well ventilated area due to the fact that it releases an Isocyanate gas when curing. (Cyanide Gas)
The foam latex you bake and is often used for Special F/X prosthetic appliances has a very little bubbles within the piece when done and is typically very flexable depending on the grade. One set back to foam latex though is that the oils from your skin break down the composition of the material. So it should be maintained with care and armoralled regularly.
Don't have any really good close-ups right now, but this one has me on the left with the cold foam dreads dunked in Monster Maker's dipping latex (though some people airbrush colored latex onto dreads as well), the one in the middle is the foam backer-rod with the tips sanded down to points, and the one on the right is cold foam without any added latex. That one has dread rings molded right into the mold.
The ones on the middle Pred are from King Jamie. He uses the polyfoam backer rod.....but a better version than the normal backer rod. Mine are from another guy who doesn't make them anymore. They were white, and E2K13 and I dunked them in dipping latex (mixed with black latex dye) and hung up to dry.
I didn't use any dread rings there, but now I'm using some.