Netherland's UA is highly situational. I had a game with them where I rolled a start that had only cotton in it... and more cotton not far off. And after that, the nearest different luxury resource was gems... and Gandhi beat me to it. In this situation, the UA is practically worthless, because I'll have to sell off the first 4 copies of cotton before I even get to the last copy. And I've had situations like this a surprising number of times as them.
On the opposite tack, I have at times rolled a start with 4 or more luxury resources within reasonable range or actually in the starting area of my first city, and in these situations, the UA does reasonably well, because I can always trade off all 4 luxuries for a set of 4 new luxuries I didn't have before, and I'll get a decent happiness boost.
Like most, if not all, UA's, Netherland's UA has its uses. And comparing them to Arabia makes sense, I can see, but there's a huge difference between being able to trade luxuries for extra happiness right away (Netherland's UA) and having to wait, tech for a while, and at last build a Bazaar (Arabia's UB).