Both work well if properly maintained... I usually run K&N, but I put on an Outerwear to help shield the filter from dust, dirt, and water.
Uni filters work great, too, and are easier to clean/dry than K&N. My '02 Blaster has a Uni filter and it does the job well. I'd choose Uni for ease of install and maintenance; you can get Outerwears for these, too.