It's impossible to give a valid answer without knowing how many items might be in the list. If it's small (a few hundred items or less) then you would be hard pressed to see any difference in throughput no matter which container you chose. Processing times really only come into play when containers get quite large, with thousands of items.

If you need to order your items in a container that isn't sequential, you can provide a comparison operator that allows the container to sort the items according to your own criteria, and/or you can add a field to your item class that keeps track of the position it would hold in a sequential list.