What are the others like in comparrison to the PD manifold??? (collins,Milltek, Ford - the orginal one that they didn't fit)

Are we talking 2-10hp or just looks better???

Also how much diff is a 4 in to 1 against a 4 into 2 into 1??? again 2 - 10 hp???

IMO if the differences between the manifolds is negligable then finding the balance of well made and good price is the way to go for me.