Neither. Both are young enough in their respective age brackets to where if it did go south, they could recover.
But in the interest of the question, if either was really taking a risk, it'd be the chick. A lot of men don't really reach their "attract a chick with the whole package" peak until their 30s. Assuming the hypothetical breh in this case has all his shyt together, he could spend a couple years with this chick and not be phased whatsoever.
Only way for this to go bad for the chick is if she ends up as a single mother (since the way the Coli tells it, that's a death sentence for any chick trying to get cuffed). But even if it were a 5-6 year relationship ... she's still 25 or 26. If she's worried about her 20s/her fun phase or whatever ... age honestly doesn't stop the heauxness. Regardless of gender. Societal norms just try to dictate when to get it out of your system. But really ... people peak at different times.