Pros and cons of crushed granite vs pea gravel as media

[Ronaldo Maximus]

I have my growbed all built up and ready to go.  I will be getting a ton of rock this weekend.  I would like some opinions as whether I should use crushed granite vs pea gravel as the media.  One advantage of crushed granite is it has nooks and crannies which provide more surface area.  A disadvantage is it has sharp edges which could cut into roots and may be hard on the hands.  I would appreciate response as to the pros and cons of both sources.

Another recommendation I have heard is to put larger media, such as 3/4" river rock, at the bottom of the growbed.  What is the advantage of this?  My concern is the law of entropy would come in to play over time and it would all get mixed up.  

Thanks for the advice!

Ronaldo

[Bob Terrell]

gravity.  if you put smaller media over larger media, the smaller media will over time migrate to the bottom.  what if you put the smaller media on bottom and put the larger media on top?