I currenly have the quad band.
I have the quad band Diamond antenna for the 8900r. it's OK, but for off-highway applications, I'm looking into getting a smaller, more flexible dual band antenna and a triplexer so I can add a dediated 6m or 10m antenna someday.
I think I'm going to sneak to HRO in Denver today to learn more about the best antenna(s) for our application. At this point, I really only need dual band (really just 2M) - but still growing into this hobby.