It depends on what your datasets looks like, and what you want/need to do with your data.

Large Arrays & ArrayLists.  Want to conserve memory and maximize performance for loops, contains, etc.

Again, it depends on your data (I didn't mean to ask what you use as current containers).
Only primitives? Objects? Fixed size or changing size? What kind of update? What kind of access? And so on.

Base arrays and array lists are quite efficients in lot of cases, both in memory usage and CPU. Except for some uses...

That's beyond my skill level.  I thought all ArrayLists were objects.  My Arrays can vary, but I have a couple large class arrays.  Looks like this..

Node[] nodes = new Node[20000];

1. class Node {
2.   // variables
3.   int id, w, x, y, z, offset, ncoffset, edgecount;
4.   int sphx, sphy, sphz, sfcx, sfcy, sfcz, startx, starty, startz;
5.   float ccval, betweenness, degree, closeness;
6.   color c;         // color (in scene, not buffer)
7.   String label, category, category2;
8.   boolean enablecat, nodefilter, exclude;
9.   int cluster = 1;
10.   String[] extras;
11.   public Node(int id, String label) {
12.     this.id = id;
13.     this.x = int(random(-width, width));
14.     this.y = int(random(-width, width));
15.     this.z = int(random(-width, width));
16.     this.betweenness = 0.0;
17.     this.degree = 0.0;
18.     this.closeness = 0.0;
19.     this.sphx = 0;
20.     this.sphy = 0;
21.     this.sphz = 0;
22.     this.sfcx = 0;
23.     this.sfcy = 0;
24.     this.sfcz = 0;
25.     this.startx = 0;
26.     this.starty = 0;
27.     this.startz = 0;
28.     this.w = 55+w;
29.     this.ccval = 0.0;
30.     this.label = label;
31.     this.c = color(1, 1, 1);
32.     this.enablecat = true;
33.     this.exclude = false;
34.     this.offset = -1;
35.     this.ncoffset = -1;
36.     this.edgecount = 1;
37.   }
38. ...
39. }

Note: except for the fields of same name than parameters, no need for the this. prefix.
And no need to initialize the fields to default value (0, 0.0, false, null).

Yes, ArrayLists (and arrays) are objects, I meant to ask if you were storing primitives (int, float, boolean, etc.) directly in your collections or only objects. And what you do with all that data.
If that's just filling the structure, and getting the data, just stick with arrays, you can't get any faster and memory efficient... (as long as its size is kept constant).