Taste-wise, the whole grain shells have a slightly grainier texture which may take some getting used to for certain people. Otherwise, the taste is nearly identical to the non-whole grain shell.
Price-wise, at my local supermarket, the whole grain shells cost about 20% more than the non-whole grain version.
With everything else being practically equal, is the slightly higher price and less desirable texture worth the extra 2 to 3 grams of dietary fiber? I would say that the answer is YES. According to the Institute of Medicine, women need approximately 25 grams of fiber while men need approximately 38 grams of fiber per day. Yet, the average American adult eats only 15 grams per day. So, it would seem that in the dietary fiber department, the average American can use all the help s/he can get!
Recipe: Incredibly Easy, Healthy and Delicious Meatless Tacos Recipe that Even Non-Vegetarians Love: A Really Tasty and Healthy Taco Recipe Incorporating Four Superfoods
Reference: How Much Fiber Do You Need?