I have both wood (or boo) cores and foam cores in comparable bows of the same make as well as having them with both kinds of cores in multiple makes of bows. The foam cores seem to be smoother, quieter and just as fast if not a little faster than wood or boo cores. Foam cores are not a quantum leap in any way, but they seem to be better in some respects. Not everyone agrees. Hoyt has been using foam core in limbs for decades, so their endurance is not a big question in some respects, but David is correct that use of the foam has not been widespread, so the data is limited. If you are not worried about the endurance or durability of fiberglass, then you probably have no good reason to worry about the foam. They are very similar and no one I know of is concerned when fiberglass is used in a bow, because most of our bows use it.
Allan