I was wondering the same thing a little while back so here is the post and responses that i got....
MW vs OB
I ended up going with a MW, mainly becuase of cost but also cos if anything was going wrong or i needed to see a specialist i have full confidence that my MW would refer me anyway. I am pleased i made that decsion and feel like i will develop a really good relationship with my MW that i mite not have had with an OB.