Try reading through this link:
http://thefertilityshop.com/catalog/...?newsdesk_id=8
It takes some patience to learn how to use them properly and there are some people that it just won't work well for. LIke women that are breast feeding or have kidney problems.
One brand is really not much different than another. The only brand I've found a minor difference in is Maybemom because it has a glass lense vs a plastic lense. But even that is not a major difference. You WILL get the same results no matter what brand you use. Some are just easier to read than others.
I've got a ton of experience with these things....so if anyone needs some guidance in using them, let me know!