It depends on the show. A lot of animation and special effects heavy shows are way better as shorter seasons with time to get things right. I also love the number of limited series that tell a complete story in 6-10 hour long episodes or even better episodes that are the length they need to be to tell that part of the story.

While some of the series with 20+ episodes churned out every year worked fine, those tended to get stretched pretty thin and while they resulted in some occasional fun one off episodes the vast majority were forgettable filler.