French Terry refers to the knit of the fabric - generally smooth on one side with loops on the other. There is also stretch terry which will contain a stretch type fabric for elasticity.
The bamboo french terry I use is milled specifically for the purpose of nappy making and incredibly absorbent for it's slimness. The bamboo is combined with cotton in the same way that hemp is for hemp french terry, hemp fleece etc.
I did an awful lot of research into soy before I started using it and, as far as I can tell, the only nappy companies using soy are those who use soy jersey. This is more of a clothing (underwear) fabric so certainly not suitable for absorbency unless you used an awful lot of it! There are no soy french terry suppliers in the UK at present although I am in talks with Elaine at Eco Earth to start stocking it. Obviously I know that means that every man and his dog can start making soy nappies but it's a great fabric and I feel we shouldn't be hogging all it's loveliness to ourselves lol!
Jenny, we are currently awaiting our next delivery (it goes so quickly!) but I might be able to spare enough for you to make some inserts. If you are interested, please pm or email me.