When I was looking for clear full length cedar last year here in on the West Coast (home of wrc), it seemed far more common to have the clear long boards quartersawn. For example, one sawmill's name is actually called "Edge Grain Cedar".

My answer to the original question is that it doesn't matter other than starting with flat sawn boards may save you time. To save more time, try to get boards that are as straight and level as possible with nice planed surfaces. The better the wood is that you start with, the easier it is to plank.

: well more than structure its a workability (right word?) issue, you would
: want to have vertical grain on the strips ideally, vertical grain strips
: come out from the cut of flatsawn and, if im not wrong, flat sawn wood its
: cheaper than the quartersawn... The point im trying to make is that if you
: look for the best flatsawn board you can find in normal stores you would
: end with the cut you want and spend less, not really worth to go buy
: furniture grade cedar just because its the best wood when, with a little
: time, you can find great boards in the fencing pile.