I've been on both twice and both has benefits. Humira stings a lot more, but seemed to help more with my stomach pain. Cimzia hurts less and you theoretically can do it less often, but I've heard most people say it doesn't last the full month for them. My drs office has had a big problem with that and has been trying people (including me) on half a dose every 2 weeks, but that doesn't seem to work as well either. I think someone on here takes the full Cimzia dose every 2 weeks, but my drs say insurance won't approve it, so I think it depends on the insurance and whether your dr is willing to put up a fight.
I maybe had less of an injection site reaction on the Cimzia, but it was nothing more than an itchy red whelt on the Humira either, so neither caused any concerns. Both have the copay assistance programs that are comparable now, I believe, so price shouldn't differentiate. They were both about the same for me. Just pick one and try it and you can always decide to try the other one later.