In terms of the information a listener would extract I don't think that there is much, if any, practical difference between the two.
Grammatically, the first example uses the present perfect tense, in which making the decision [to watch the show] occurred at an unspecified point in the past and may still have relevance in the present. The second example uses the past indicative tense but does not specify a point in time any more than the first example and does not suggest direct relevance to the present.
I personally would prefer the first example in cases where I am still watching the show or otherwise currently engaging with it in some way, and the second in a case where I've watched every episode and no longer engage with the show in any way. However, if I were trying to express those ideas I would not rely on verb tense alone like this to convey my meaning.