Personaly i think it has a lot to do with how the bristles retain water & how good the flow is through them.
I tried a crinkle mono & the bristles were actually water repellent, the brush was bone dry after use. so for rinsing you were actually only using 2 x 2mm jets of water as the bristles held no water in them at all. The results were rubbish.
The vikan mono does have a minor issue of being a tad too stiff IMO, but is an excellent all round brush, it retains enough water to clean well & if jetted correctly allows a perfect flow. I've used mine for around 10/11 months & never changed back to anything else yet. the vikan mono does get better the more you use it mind.
The vikan flocked is also a top brush IMO, both are better when the excess plastic stock is trimmed off them too. Only rectangular ones though, i'm not fond of any oval brush!

Tony