CNA/NNOC have a history of raiding other unions. They did it in Hawaii and Mass. They have in the past (in my personal experience in Hawaii) lied to gain entrance to meetings, tried to represent themselves as members of the Hawaii Nurses' Association (HNA) in order to vote at a House of Delegates, paid prior CNA board members to infiltrate (HNA), they illegally masterminded a takeover of the HNA - it should be noted that was the determination of Federal District Judge Gilmore, who ordered CNA to immediately vacate HNA's premises, and many other instances of either illegal, unethical or questionable activities in trying to reach their goals. There was also an NLRB hearing in California that found CNA had illegally harassds and threatened nurses who were opposing their efforts to organize their facilities.
Instead of focusing their energies on organizing those markets that are not unionized, they try to take over another union. And, it wouldn't be so bad if they came in announced that they thought they would represent the nurses better and up front tried to convince nurses to change unions, but instead, they resort to the methods above.
This, in my opinion, reduces their credability, and forces nurses to pick an apparently more ethical organization or one that may be able to make better contracts but suffers from a lack of moral conscious. As I said, these actions could tarnish the reputation of nurses who are perceived as holding high moral and ethical positions.
Besides that, some of the articles below (which were found in a very quick search of the net, the list is certainly not exhaustive) point out that CNA has it's detractors and may have concerns over how it spends it's, or should I say it's member's money.
Again, all I am saying is that both ANA and CNA/NNOC have their own issues, and as organizations, it will be their members, thru their actions or inactions, that will shape both the direction and operations of those organizations.
IMHO, if you choose CNA/NNOC as your organization, you will need to ensure that such practices as noted above are curtailed. If you (hypothetically speaking of course) choose ANA, you will have to ensure that the needs of the bedside nurse are made a priority and wrest control from the educators and management-types. Either way, it will be a difficult job, and you will need to get buy-in and participation from other nurses. Good luck.