For your racing, the K&N (gauze) style would work fine.  For running in the sand, the gauze style doesn't filter the fine dust (or even the small sand particles).

The Uni Dual Layer is a great filter for sand dunes.  I was running a 4x8 monster on there, but dropped down to a 4x6 as it doesn't flop around as much with no rear support.

So in short, the K&N should be fine for your runs..... especially since it looks like your in the lead most of the time