n400journey

ROC stands for Removal Of Conditions. For people that apply before they've been married for 2 years, they get a conditional green card good for only 2 year. At 2 years they have to apply again to remove conditions and get the 10 year green card.
Since you say you've been married for 13 years and got green card 6 years ago, you probably didn't have to go through this step.

You can apply under either rule. The 5 year rule is easier.
Since you got your green card through marriage you may be asked about your marriage and you should take supporting documents just in case, but as a 5 year applicant, the issue will probably not come up unless there's some reason to question the marriage. For instance if you are now divorced you may be asked how soon after ROC you were divorced.