Mostly because of English series having a lot of word plays that get literally translated to Dutch, completely missing the joke.
What also looks stupid is when words get spelled out. "ontslagen" is Dutch for "fired", so "You're fired! F-I-R-E-D!" gets subbed to "Je bent ontslagen! O-N-T-S-L-A-G-E-N". I get that's supposed to happen, but I think it looks ridiculous.
So ye, I prefer English subs, because of that reason and also because I'm used to it.