Softball4life, It sounds to me like you will be using track or cross country to inhance your speed and endurance for softball.
If this is the case and your not entering either one for just the competion , then I dont believe that either one would be a bad idea being that your real interest is in the training end of it. As far as cross country goes , if you have a good coach and you are running 2 to 3 miles a day durring training , how can this not be building strength , stamina , endurance , and muscle??? My DD ran cross country this past fall and it was all about personal achievment. By the end of the cross country season she and her teamates had out done themselves in many different ways. Some had improved on their time , some the distance they were able to run , their breathing , the way they use their bodies to run , etc.etc.etc. I feel confident in saying that these achievments will carry onto the softball field. In reference to the Athletic Trainers advise on never reaching max speed because most plays happen within 1-3 secs. I dont look forward to telling my player that just hit a double , tripple , or in the park home run that she never really reached her maximum speed rounding the bases. Point to the thread , if you can do both , do it. If you have to pick one , pick the one that best fits the type of training your body needs to better yourself on the field. Either way , enjoy what your doing and with all heart commit yourself to getting to a new level.