It will come down to $/acre.  There are no technical barriers to either approach.  I tend to not want to rely on third parties for data/analysis (aside from nutrient measurements).

Near instant stitching:
http://dronemapper.com/

Plenty other competing for this market - likely decent open source stitching packages to be available in the near future.  You must see UAV's as near disposable.  You should not pay more than a few hundred dollars for them or the camera. 

 http://publiclab.org/wiki/infragram