I run the air bags. Gives you the ability to adjust the height for different weight situations and seems to ride better. I've run them on the last two trucks and been very pleased. I've never been a big fan of 'Add a leaf's".
I think the basic 5000lb airbag set-up is around $200 and install is a snap. Check SummitRacing.com, they seemed to have the best prices around.
BTW, truck looks good, congrats
Chris