There are a myriad of opinions about rain gear. Just read any thread about recommended rain jackets. There are some truths to be distilled, however. I think pretty much anyone would agree that rain pants are good to have in temperatures below 50 degrees Fahrenheit. Well, there's always the exception to the rule.
I'd look at the range temperatures likely encountered and make my judgment from there. I've heard Skurka speak about good trip planning and he has a very left-brained approach that can help tailor your gear to the expected conditions.
I like good quality, well cut pants that have short zippers so that I can put them on and take them off conveniently. I will say that in my region (Southern Appalachians) I rarely bring them. Only in the shoulder seasons would l consider them worth bringing. My legs generate a lot of heat while moving and at camp I wear a base layer.