Truthfully- neither. While TV shows are better suited for story telling format for comics, the flip side is if the writing staff is capable of translating from the book to the show well or in most major cases- will the small TV budget allow for stories/special fx to tell epic sized storylines.
Where as with a movie, the budget is there(most those type movies have a cost well north of $175 million), but you have to condense your story into a 2-3 hour format; therefore the story cant be told at the pace that it needs to be and a lot of stuff gets sacrificed- even with trilogies.
Also not to mention in both platforms there is also the issue of creative control. With TV shows, the creator may retain a little more control, but with most movies the creator usually loses control(and in some cases, it was a good thing as the creators were not equipped to deal with the process of their work being transformed into a movie or trilogy franchise).