[markisus]

Everything is a tradeoff. Even things like goto, and global variables will occasionally be the right choice.

Regarding the std::vector method, you may have a very loosely coupled system where a bunch of T1's enter into a pipeline and come out as T2's. For this use case, std::vector<T1> and std::vector<T2> are great. On the other hand, if you need to create an object and hand it off to someone else with no knowledge of how long they will need to hold onto it, then std::shared_ptr could be a good option.

In the in-between you have entity component systems that do the type of index tracking you mention so that identities are decoupled from memory location, allowing objects to move. I didn't understand your point about global variables and why they are necessary to implement this type of system. I also didn't understand how this gives up on all ownership. The owner would be the system that maintains the index to memory location mapping.