Arraylists uses dynamic arrays under the hood which makes them slow for data manipulation (although fast for storage and retrieval). For instance, deleting an element in ArrayList will cause a bit-wise shift in memory. On the other hand, LinkedList is implemented as nodes with one node leading to the next or previous (in the case of a doubly-linked list). This makes them faster in data manipulation. For example, data deletion requires reconnecting the next and previous pointers to eliminate the deleted node.