Pine straw is a great alternative to using mulch in your landscape. Both are pretty close from an expense standpoint so it really comes down to your personal opinion. Pine straw tends to not wash away in your beds as easy once it has settled and matted down. The layer also offers a good weed barrier and helps insulate the beds during the winter. Another thing to consider is the type of trees in your area already. If you have several pine trees in your yard then it would make sense to use pine straw. You would end up with mulch beds that just get covered once the needles start to drop. Just like mulch though, pine straw will fade and break down over time and need to be replaced. At the end of the day however it is just your choice and what you think looks best.