The only way you will notice the difference of geometry between the two is by having used one and then changed to the other
If you start out on Exo's you will not even know the difference
I have used Skip frames with Skip springs and with PJ springs
I have also used Exo's and Exo-Pro's
I even had a set of 7's once
I now use a set of Skip frames with Exo springs on them (The perfect bock for me)
The Exo spring is far better for me than any other I have tried
The simple answer is to listen to Paul-Self he should know (If you ever see him bock you will realise why
)
One last reason is that you can buy 4 pair of Exo-Pro's for the cost of one set of Skips
Jason