I guess this is one of those questions like "What Came First, The Chicken or The Egg"? The standard field points with the PSE TAC15
Arrows are always 85 grain heads, give or take a few grains here and there. This means that one can easily purchase Broadheads to match this weight or you can purchase Field Points in a heavier weight to match the Broadheads you are planning to use.
It doesn't matter which way you go as long as you understand the two different styles of points should always match. Once you get involved in insuring that you are shooting a specific F.O.C. (Front of Center) balance on your arrows, then adding or deleting some front end weight makes a difference.
If shooting the PSE TAC15
arrows, it's recommended to maintain an F.O.C. of about 10% - 15% for hunting purposes. This equates to a 100 grain arrow point. Target shooters usually balance the F.O.C. on their arrows at 5% - 8% and the 85 grain points fall right into this category, so depending upon what you're using your crossbow for will depend on what point weight best suits your needs.
Hope this helps you understand the differences.