This is the order I have most success with:
Pool (by far), Namewinner, Enom, Godaddy
I dont use any Snapnames derivative...
If I have put a backorder on a name, at ALL of these, then Pool has won 90 pct of them.
I only use pool if the name is definately worth $60+ (reseller) in my opinion.
Enom + Godaddy are now the cheapest since Namewinner raised their pricing.