Hi Jim W,
Every one pretty much read my mind on this one and the posts were very accurate. Brad is right. The biggest reason is the cost. The Fostex drivers fit my price points very well. I want to keep the cost as low as i can and the Fostex drivers let me do this.
I have heard other drivers including the Supravox and I still come back to the Fostex. In terms of sound, price and amazing build quality, they are hard to beat.
Greg and JLM are right about Lowthers being better loaded in backhorns than BR. The Lowthers are not suited for BR and they have that shout rosypup mentioned which is very hard to tame.