From what I have read, spoke pattern has almost no effect on the vertical stiffness and strength of the wheel (less than 5% difference between 3 cross and radial).

Based on this analysis: http://www.astounding.org.uk/ian/wheel/patterns.html

Where it matters is in torsional stiffness. For a touring bike, the main load is vertical load, so lacing pattern shouldn't affect things much. Having more spokes of course makes the wheel stronger.