Chris makes a good argument that watching something as it was originally intended to be watched is preferable. But I also posit that when the animators are making these shows, they are not doing so thinking that people will be reading lines of text at the bottom of the screen at the same time. In that sense, I feel that dubbing it in the language of a viewer is getting closer to how something is "intended to be watched."
An interesting argument, but I don't agree. Anime is not some kind of special category here. Foreign films have been subtitled for decades and will continue to be in the future. It's a slight accommodation to overcome the language barrier, as opposed to changing the language altogether.
I wonder if this argument comes along on the same line as the dubbing issue: there are many Tokusatsu fans (myself included) praying for their favorite soundtracks to be sold on iTunes. However, the moment when that announcement was made (referring to the recent Gokaiger & Super Sentai Soundtrack), some of them complains about going to iTunes. Just can't please everyone, "to dub or not to dub" can also be said as "to iTunes or not to iTunes".