[MetalMan]

The FMA packs are the only ones offered as a complete (expensive) system that will monitor and control everything. If you buy another brand of battery, and buy a charger, a balancer, and a LVC device, it will be compatible with other batteries as well (as long as they have the same balancing connector). The FMA packs and devices only work with each other, and the packs cost a lot. But since money was already initially spent with them, you might be unwilling to go with another (potentially) better battery.

For people like me that are looking for the most cost-effective system, and that already have a charger and LVC, stand-alone packs (or home-made ones) are much better. I would only reccommend the FMA packs to those just entering the LiPo scene that have no knowledge of it but desire the advantages.