reefermedic hit the nail on the head.
Everyone has a different belief.
I have had all etss's under the 800,a euroreef,asm and now octopuss 200.
My opinion is same as reefermedic,that the downdraft and needlewheel seem to pull different kinds of skimmate.
Example,my last 75 reef has had a euroreef etss 500,etss600,euroreef rs80,asm g-3 and octopuss 200.
(yes I change my mind too much)
the needlewheels pull real smelly tea colored stuff and skim wet
The downdrafts pull dry stuff that doesn't smell half as bad but is much darker brownish.
To me the best bang for your buck out of them is the octopuss 200.
best performance seemed to be the octopuss 200 also,after grinding open the elbow,pump outlet,air inlet,mesh modding and recirc mod.
soynd like alot of mods but takes less than half hour to do.
I am actually going to build my own skimmer that will be similar to the new etss sump buddies but will incorparate a recirc needlewheel also.
best of both worlds
hope this helps.