Answer:
Nitrogen A would be more nucleophilicity (figure 1.)
Explanation:
In the DMAP molecule we will have 2 nitrogens label as "nitrogen A" and "nitrogen B". For nitrogen B we will have more steric hindrance due to the 2 methyls groups and the benzene ring. What will hinder the attack from this nitrogen (nitrogen B) to an electrophile. On the contrary, the attack of nitrogen A could easily occur.
