Some anime's are good with english dubbing and some aren't due to poor dubbing or just not fitting it right, I personally find that if i have seen an anime with english dubbing and some of it (a special movie etc) is not available in the english dub I find it odd and takes away from the whole experience, thats why I have started checking if all aspects of a series are available in english or if they are not, if they aren't I will generally watch it subbed.