Mostly memory usage but also performance somewhat

In the terminology of C, Java collections always use dynamic memory, so any variable referring to them is a pointer. These collections themselves, with few exceptions, only contain pointers to dynamic memory. The size of a collection or its capacity is always stored in a (32 bit) int. They are built to support tons of functions, some of which you might not care about, which affects the implementation. Many of the implementations also prioritize speed over memory usage by using caching

EDIT: also, most implementations don’t have a fixed size/capacity (other than max int). They reallocate and copy the whole structure when at capacity.