What is the difference between a 3-pc 8-Spline crankset and just a 3-pc crankset?

Question

which is better for bmx.

Answer 1

The 8 spline refers to the way the cranks are connected to the bottom bracket.  The first link is showing a 8 spline bottom bracket and the second one is showing the square taper style.

You will find the higher quality bikes will have the 8 spline shafts, but there is nothing wrong with the square taper.

For BMX go with the 8 spline.

Answer 2

If your purpose is using a bicycle for just everyday ridng a three-piece will serve you well for now.  If you arre planning on doing high impact and hard use tricks and have spare $, go with the splined.  Either way, let me say your feet will never know the difference.