Radial ATV tires will ride smoother and last longer than their bias tire counterparts.  This is especially true with those who ride trails and hard pack frequently.  Simply stated, bias type atv tires will wear out quickly when ridden on these types of surfaces.

Typically, radials will not have quite as deep of lug or be quite as wide as bias tires, however they are more efficient in producing traction through the contact patch.  Radial tires are more expensive to produce than bias tires, but the advantages are increased tire life (up to 2 or 3 times), better ride quality, improved fuel efficiency, and less rolling resistance.  The bottom line: consider radials if you are riding many miles or looking for tires that will last longer.