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.