Poppet just my opinion as an approved adopter who is not yet matched I can't (personally) see any benefit with a voluntary agency. I would be very happy for anyone who has been with a voluntary agency to tell me why they are better.
Some people I know chose voluntary agencies, but I do not know why.
we chose our local authority because they have children to place.
If you are near a border you could talk to all the local authorities and voluntary agencies near you (actually you could do that even if you are in the middle of a county).
Also I would just consider where you live in the county. For example. A county can't place children near where their birth families live, so a very small county or one with few cities/towns might be less appealing to you if you live there in one of the towns because all the children from that town could not be placed with you. If you were out of county or in a big county you may do better. Does that make sense?
Also, any county can only tell you what the situation is like now, or what they think it will be like, but not actually what it will be like in 6 months or a year when you are hopefully approved.
I think I am right in saying the county that has the child in is responsible for proving any support for 3 years so if you adopt from a county very far away this might be harder to access support from, but actuary some may not offer much support anyway. So a larger county quite close to you could be a good bet for having more children and for being able to place them with you if are you far enough away and yet not being too far away to access support if you need it!
Phew, does any of that make sense?
Just a disclaimer I am relative newbie myself but I hope someone will come along and confirm what I say and that I have not got the wrong end of the stick.
Best of luck.