Now you are comparing and in tank skimmer to an external skimmer. I understand your concern, I had a skimmer before that had flat gaskets and a half dozen screws to take off everytime I cleaned out the collection cup. I had trouble getting it to seal and not drip water.
This skimmer has o-ring...
Another approach to improve a skimmer performance is to buy a less expense skimmer and modify it. The one in the picture is a modified ER 5-3 with 18" section added to the bottom along with a larger recirculation pump. It performs super. It remove a half gallon per week of black goop.
