It's really a question of "price" and "value" when looking for a new balancer. The OEM Ford unit will cost less "per unit" than a BHJ. They are becoming scarce from what I hear so it may not be easy to find a NEW one. The real issue is reliability. The OEM comes with the pulley attached, but I'm not convinced that it is actually Zero-Balanced as a unit when you get it. I had a new OEM break within a year of install. If you go the OEM route, I suggest that you have it checked for zero-balance at a machine shop and then install it with a NEW bolt at the specified amount of torque. Once its on, never remove and reuse it or you will be on borrowed time. There is still no guarantee that the new stocker won't fail down the road (literally) and need to be replaced. The BHJ, on the other hand, is more expensive to buy, but it is a high quality unit that will not break because of the superior design and materials. You will need to get a zero-balanced pulley (or have your stock pulley balanced with the BHJ), so that additional cost is about the same with either unit. The BHJ can be reused if it is ever necessary to remove it. I broke 3 stock units (2 new, 1 used) before I got my BHJ in the original "group buy". I think that was back in 2001 and have had no problems since then.
For my money, the extra $100 or so was well worth it to never have to deal with the balancer issue again...