You guys are missing the point. Yes there is a difference, more expensive model may actually skim better:
However the point is: the difference in performance number 1 is very minor. The best skimmer tested was 30 effective in removing DOCs and the majority where ~25%. A difference of 5% doesn't account for a whole lot when both at the end of the day still proably removed about the same amount because as the DOC levels decrease so does production.
Number 2, the difference in effective DOC removal certainly doesn't account for a 500$ price difference.
In conclusion:
When shopping for a new skimmer you need to evaluate more than performance. You need to look at price, pump, build quality and rated volume in that order.
To better illustrate my point. I have a 180 reef and ran it for a year with a Super Reef Octopus-1000 Internal 5" skimmer. I upgraded to a SRO-5000 10" skimmer, much much larger skimmer. At the end of each day both pulled roughly the same amount of skimm, the 10" was a bit darker maybe but not by much. The 10" may have the capacity to handle more but it made no difference in my system. Consider that when researching skimmers. There is a limit to how much any skimmer can remove no matter what and buying a skimmer with a similar rating but 5% more effective probably will not make any difference in your system.
Of course every system is different and needs are different but I needed to make this point.
The guy Jeff, from Lifereef told me that skimmers these days, with needlewheels, make bubbles to small, so they pop prematurely. He said he talked with skimmer manufactures at shows about this and they agreed with him but have to keep coming up with something new.
Also, that report puts different types of skimming methods against each other, not really skimmers using the same method. And fwiw, a 5" skimmer on a 180 is way to small, by a large margin. The reason your 10" is probably pulling darker is because the 5" misses so much, but like you said, not enough to impact the tank. My first saltwater tank didn't even use a skimmer!
It is said to match the skimmer to the tank. But when you have 1,400 gallons of flow draining, you would need almost a 10" or multi-pump skimmer to keep up. I think the reason skimmers don't do as well as they should is because most of the Sicce pumps in all of them only handle a small fraction of the water flowing by.
And yes, build quality with the skimmer is a huge part in the decision making. As I said, I was looking at the Reef Octopus Elite 200, currently their best skimmer line out, and there's the internal version with the external pump for $599, and the the space saving model for $799. I emailed CoralVue about why a space saving skimmer that produces less than an external pump skimmer (because of contact time) would be $200 more. They said it's because of the extra parts needed for the space saver. If that wasn't a load of crap! It's because they made the internal one so wide it won't fit most sumps and almost force you to the space saver. Luckily the internal will just barely fit my sump. I don't even need the dc pump it comes with. Imo, dc pumps are completely unnecessary on skimmers. The Elite is basically a clone of the Vertex with a dc pump and I think the pump is what adds most of the dollar value.
But yes, I base the cost on everything, not just performance. A lot has to do with after sale support. I'm not even a Reef Octopus fan. I was first considering the Icecap skimmer, also CoralVue but not RO, but the gph was too low for the size.
I have a FOWLR tank so I need more skim to get more pee out, especially in a heavy bioload situation.
