Shockwave will allow you to keep all your settings when you change the battery. That alone is worth it to me. Plus it is inexpensive!
All brand new Axe's are shipping with the shockwaves stock now.
The shockwave's ability to save setting is very important. The use of the trigger to changes the settings vs. that older little button also saves time.
One of the biggest changes in my opinion was with the ramping logic. The older board seemed to "run away" a lot while ramping. The shockwave was much better in that regard. If you play tournies, I'd get the shockwave as it'll lessen the risk of a gun penalty.