The only difference I think is that with the 4000 stack you can call just a little bit looser with position so you can put people's stacks to the test.

ex:
MP2 raises to 75, you call with JsTs in the CO, flop comes 9sqc4c, MP2 bets 150, you can raise to 400 and fold to an AI. As another 1000 stack, it might not be worth it to get involved with a speculative at all.

It's not much of a difference since it's really really situationally dependent, but it is a difference.